Figuring loads / block & tackle theory
 

In article ,
says...
(Doug Miller) wrote in message gy.com...

snip

Wrong. The tension on both sides will be equal (20 lbs) and the top
hook will feel 40lbs. There is nothing being added to the 40 lbs to
increase it to 80. I think you have confused the effect of a pulley
which, when rigged right, will cut the lifting force by 1/2.

It appears that *you* are the confused one here. A *movable* pulley will cut
the lifting force in half. A *fixed* pulley only changes the direction in
which the force is applied -- and this situation is entirely analogous to a
fixed pulley.

Exactly what I said if you read it. "when rigged right"


--------40----top-------------
/\
/ \
20/ \20
/ \
load/40 \anchor
------------bottom-------

Nope. You have a major problem he on the left side, a 40-lb weight is
suspended on a rope that has only 20 lbs tension. Doesn't work that way.

Suppose the anchor on the right is replaced by an un-anchored weight. What
weight is required on the right to balance the 40 lb weight on the left?
According to your diagram, the answer is 20 lbs. Now do you see your error?

--------------------top--------------
\anchor /anchor or pulley
\ /
\20 /20
\ /
\ /
\/
40
load with pulley
--------------------bottom----------

Not the same situation.

Of course not. That is the correct way to rig to cut the load by
half.

And now after my other posts I am confused. Having nothing much to do
I went to town and got two fishing spring scales and rigged a couple
experiments.
hook 22lbs
/ \
/ \
/ \
bal / \ balance read from 11 to 18 lb
22 / \ depending on how I adjusted it due to friction
over hook.
/ \
/ \
/ \
22lb water anchor

"Balance read from 11 to 18 lb depending on how I adjusted it".

That's one of the things I was referring to when I said your numbers were
"all over the map" and when I said that your so-called experiments
(assuming you actually did any) proved nothing beyond your own inability
to take accurate measurements.

The second experiment replaced the hook with a snatch block.
I got 22 lbs on the left and 20 to 21 lbs on the right (I was sorta
expecting readings about half but wasn't surprised)

Why are you measuring the loads in the individual segments of the rope?
We're arguing about the load at the hook at the top.

Third put the snatch block on the bucket as in my 2nd diagram above.
Weight of bucket/water/snatch block now 26lbs.

Readings 14 lbs both left and right as expected considering the crude
tools I am working with.

Your inability to take accurate measurements again. Fishing scales are
pretty accurate (as you would know if you had ever actually used one).

My confustion is trying to understand how, in the first experiment we
have 22lbs left, 22 lbs top and 22 (approx) right.

How did you measure in three places with only two scales? Methinks this
"experiment" is a figment of your imagination.

Somehow it looks
like 22 lbs are magically appearing on the right.

ROTFLMAO! "Magically appearing"!!

No, the strain on
the hook is not 44 lbs altho it would be if I were to han 22 lbs on
the right to balance the load.

On what do you base your claim that "the strain on the hook is not 44
lbs"? Indeed, on what do you base *any* claims about what the strain on
the hook reads? According to your own description above, you never
measured it!

Figuring loads / block & tackle theory
 

In article ,
says...
(Chris Lewis) wrote in message ...
According to :
Harry K wrote:
Don't bother, he won't believe you but just to prove it -again- I just
re-ran the experiment. Bucket weighed 26 lbs this time


scale reads 26 (taa daa!)
I\
I \
I \
I \
I \
I \
I \
bucket anchor
26 lb

Again he won't believe it and refuses to do the same experiment

You are either lying, or you've tied off the rope to the scale and the
anchor isn't doing anything, or possibly you don't have the scale in the
right place.

Or he anchored it to the bucket...


Hey, good point!. In practice it doesn't matter if the rope is
attached to an anchor or tied back to the bucket. The result is the
same. No forces are changed and the bucket remains in place. Think
about it.

But it *does* matter. The forces *are* changed, and the result is *not*
the same -- as you would know, if you ever conducted the test that you
keep challenging others to do.

The scale will read 52 lbs assuming it's between the hook and the rope,
and the rope is free to slide such that it needs to be tied off.

Right.


Yep, and that is just how I rigged it, scale from hook to rope and I
eased the rope on the scale several times before reading. Try it
yourself. It will only take you a minute.

If you actually conducted the test, rigged as you show in your diagram
above, then you're lying about the reading on the scale.

Figuring loads / block & tackle theory
 

In article ,
says...
[big snip]

Someone way up thread posted at link to a site
giving the good explanation.

Once again, Harry, you're caught in a lie. The site posted does *not*
support your position here, despite your false claim that it does.
Here's the relevant part of the post you refer to:

http://www.howstuffworks.com/pulley.htm

This web page speaks to the issue of how much pull is needed on the rope
to make the weight go up. But it does not adress the felt weight on the
pulley hook.

Note that last sentence, Harry: "does not adress [sic] the weight on the
hook".

Figuring loads / block & tackle theory
 

Figuring loads / block & tackle theory
 

Figuring loads / block & tackle theory
 

Figuring loads / block & tackle theory
 

"Harry K" wrote in message
om...

HOOK
scale 22 to 22.5
I
I
I
I
I
Bucket 21.5 lbs



THIS IS NOT THE EXPERIMENT WE ARE DISSCUSSING!!
Greg

Figuring loads / block & tackle theory
 

"Harry K" wrote in message
m...


Hey, good point!. In practice it doesn't matter if the rope is
attached to an anchor or tied back to the bucket. The result is the
same. No forces are changed and the bucket remains in place. Think
about it.




YES!! YES!! YES IT DOES!!
It makes ALL the differance in the world where you fasten the "loose" end of
the rope!! The results are NOT the same!
If you fasten the rope back to the 40 lbs bucket you esentially have two
ropes, supporting 20 lbs each!!

(Funny, if you think about it, because you have one rope with 20 lbs of
force being balanced by another rope tied back to the same bucket, that has
20 lbs of force! And 40 lbs at the ceiling. Pretty much what we have said
all along, just the weights are halved!)

If you fasten the rope to another anchor point, the wall for example you
have changed the whole "experiment"! You now have ONE rope supporting all 40
lbs, plus an opposing force of 40 lbs balancing the bucket, which in turn
gives you 80 lbs at the pulley!
Greg

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
(Doug Miller) wrote in message
. com...
Your turn or are you still scared?? I don't understand adamant
refusal to do a 1 minute test.

I've done the test already. I don't understand your persistent challenge to
do
something that I've already done.

If you are correct you win easily.
Just remember not to lie as anyone can check it in less than a minute.

he difference here, Harry, is that I've actually *done* the test that I
claimed to have done, and posted the results that I actually got -- unlike
you.

But just to shut you up, I did it again. Here are the particulars:

Toolbox suspended directly from the spring scale: scale reads 28 lbs. Scale
is
one used for measuring the draw weight of hunting bows, and is accurate only
to within a couple of pounds -- but close enough to tell the difference
between theory and your claims, when using a 28-pound weight.

Toolbox suspended from a rope passed through the hook on the scale, and free
to move. Opposite end of rope tied to the base of a 350-pound wood shaper so
it won't move. Point of attachment of rope is 52" below the hook on the
scale,
and offset 13" laterally. The rope is thus at an angle of atan(52/13) = 76
degrees. Theory predicts that the vertical component of the load in the rope
is 28 lb * sine(76) = 27 lbs thus the total theoretical vertical load on the
scale is 55 lb. The predicted load would be somewhat less than the
theoretical
value, due to several factors including friction losses between the rope and
the hook of the scale, internal stretching in the rope, and inherent
inaccuracies in the scale.

The actual measured reading is 44 lbs, or 80% of the theoretical value and
certainly more than 80% of the predicted value.

According to you, Harry, it should have read 28 lbs.

You are either lying about your results, or lying about having conducted any
tests at all. It's already proven that you have lied about not reading my
post
describing my test. As a _proven_liar_, Harry, the only way you can possibly
restore a shred of anything resembling credibility is to post a photograph of

your test setup.

I'm waiting to see it.

I would have posted a picture but for two reasons. 1. You can't post
a picture here and 2. I don't have a digital camera.

How convenient for you.

Why didn't you
post a picture somewhere?

I don't have to prove anything -- everyone else who has done the test gets
results that agree with mine, and with theory. You are the one claiming that
everyone else is wrong. The burden of proof is on you.

Why are you lying Doug? I told you it was pointless as anyone can
repeat the experiment in a minute. I did it this morning but again
you claimed I was measuring directly not over the scale hook although
I even said I eased the rope over it.

Harry, *you* are the one lying, not me. You never conducted the test you claim
to have conducted.

I actually went to the library this morning hoping for a book. This
is a small town 3000 population so poor selection. I only found two
that discussed pulleys, both only mentioned class 1, both disussed
class 2. Neither mentioned the strain on the hook.

How convenient for you.

I did my research,

Really. How about a web site? You've been challenged repeatedly to provide any
published source that backs up your claims. You keep saying "any physics
book", well, it's time to find one, Harry. Maybe if you actually *read* one,
you'll figure out why you're all wet.

where is yours?

My research is already posted: my test results.

Your lie about the test results does not count. My
test results are real, not made up to support apriori beliefs.

You're a liar, Harry, a proven liar several times:
- you claimed you never saw my initial post, but you responded to it
- you claimed that the web site posted earlier in the thread supports you, but
it doesn't
- you claimed to have conducted the test and recorded results that contradict
theory.

Note that my first post in the thread explicitly states that my a priori
belief was that the load on the hook couldn't possibly be double that of the
weight. Note also that when experimental evidence contradicted that a priori
belief, I abandoned the belief.

You have abandoned the truth.

I have
another plan to get a basic text book, hopefully it will work out and
the strain on hook question will be mentioned.

With all your prattling about physics books, I would have thought that you had
one already. Convenient for you that you don't.

One cite, Harry, just one cite, of a published work that supports your claims.
Where is it?

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
(Doug Miller) wrote in message
. com...
In article ,
(Harry K) wrote:
(Doug Miller) wrote in message
. com...
In article ,
(Harry K) wrote:

bunch more snippage


This part you have right but it has nothing to do with the pulley
problem.

Reread your high school physics text a few more times, until you
understand
that it is the _same_.

I do not understand you and Greg and now Steve. The test is a simple
one, anyone can do it and it will prove all three of you are wrong.
Why do you not do it. Yes, yes I know. 'I know what I know and don't
confuse me with facts'

I have done the test, Harry. It proves you wrong. Read my first post in
this
thread: I began with the same preconceived notion that you did. The
difference is that when experimental results contradicted that
preconceived
notion, I abandoned it, whereas you insist on clinging to it.

Ignorance - not knowing something

You began here...

Stupidity - refusing to learn when led to the source.

.. and are now here.

Do the test then get back to the thread. Also see below where I did
repeat the test using only one scale this time thus eliminating one
variation.

Harry, I really have to wonder if you have actually read ANY of the posts
that
you have responded to.

I HAVE ALREADY DONE THE TEST. IT PROVES YOU WRONG.

Shouting does not increase the believability of a lie. You didn't do
it, I have, 3 times now and every result matches what physics texts
say. Where are your diagrams and readings?

You're a proven liar, Harry.

I see you still refuse to address why you say my readings in the first
test are wrong. Oh I know why. Because it says that the strain on
the hook is 22 lbs when you just -know- it has to be 44. Your only
out is to claim error of instrument, reading or procedure.
Unfortunately it wasn't nor is it in the next two tests.

You're a proven liar, Harry. You haven't done the tests at all.

I haven't decided yet but I just may go to the local library and give
you a specific cite.

Translation: you're still trying to find a book that supports your lies.

By the way, You are the one who claimed I am
mistaken in your first or second post. By protocol it is -you- who
should be doing the research.

Go back and read the threads. I was the first to post actual test results in
this thread. You are making claims that contradict actual experimental
results
and it is thus up to *you* to substantiate your claims.

Post a photo of your tests, Harry -- that's the only way anyone will ever
believe that you actually did it.

Okay, I will borrow a camera. Now someone will have to tell me
-where and how- to post the picture

Try alt.test.binaries

How to post the picture depends on what software you're using to read and
post. You're on your own there, since I don't know what you have.

and it will include the scale
reading.

It had better!

It will have to be in two pictures as the scale reading will
have to be a close up.

Make sure that the position of the pointer on the scale is visible, even if
the markings are not, in the photo that shows the whole setup.

You, of course, will then claim that I am
taking the picture of the scale from a different set-up.

I'll reserve judgement on that until I see the photo.

I'm not gonna hold my breath waiting for it.

Figuring loads / block & tackle theory
 

In article , "Greg O" wrote:

"Harry K" wrote in message
. com...

HOOK
scale 22 to 22.5
I
I
I
I
I
Bucket 21.5 lbs



THIS IS NOT THE EXPERIMENT WE ARE DISSCUSSING!!

He knows that. But he can't find any other way to justify the ridiculous
claims that he's been making.
Greg

Figuring loads / block & tackle theory
 

In article , "Greg O" wrote:

"Harry K" wrote in message
om...


Hey, good point!. In practice it doesn't matter if the rope is
attached to an anchor or tied back to the bucket. The result is the
same. No forces are changed and the bucket remains in place. Think
about it.




YES!! YES!! YES IT DOES!!
It makes ALL the differance in the world where you fasten the "loose" end of
the rope!! The results are NOT the same!
If you fasten the rope back to the 40 lbs bucket you esentially have two
ropes, supporting 20 lbs each!!

(Funny, if you think about it, because you have one rope with 20 lbs of
force being balanced by another rope tied back to the same bucket, that has
20 lbs of force! And 40 lbs at the ceiling. Pretty much what we have said
all along, just the weights are halved!)

If you fasten the rope to another anchor point, the wall for example you
have changed the whole "experiment"! You now have ONE rope supporting all 40
lbs, plus an opposing force of 40 lbs balancing the bucket, which in turn
gives you 80 lbs at the pulley!
Greg

You know that, I know that, Mike knows that -- by this time, even Harry knows
it. But he'll never admit it, not after having gone to such great lengths to
assert the contrary.

Figuring loads / block & tackle theory
 

Douglas and Rosemarie Miller wrote in message gy.com...
In article ,
says...
[big snip]

Someone way up thread posted at link to a site
giving the good explanation.

Once again, Harry, you're caught in a lie. The site posted does *not*
support your position here, despite your false claim that it does.
Here's the relevant part of the post you refer to:

http://www.howstuffworks.com/pulley.htm

This web page speaks to the issue of how much pull is needed on the rope
to make the weight go up. But it does not adress the felt weight on the
pulley hook.

Note that last sentence, Harry: "does not adress [sic] the weight on the
hook".


And just where did I say that it did? I said that someone had posted
a link, you found it. I didn't read it.

Harry K

Figuring loads / block & tackle theory
 

In article ,
Harry K wrote:
(John Cochran) wrote in message ...

SNIP

No it isn't. If you tie the other end of the rope to the load instead
of the anchor, this is what you get.


|
|
O
| |
| |
| |
This half ----- | | --- This half of the rope has 20 lbs of tension.
of the rope | |
has 20lbs of | |
tension | |
| |
+---+-+--+
| 40 lbs |
+--------+


For the situition that you have


|
|
O\
| \
| \
This half ------ | \ --- This half of the rope has 40 lbs of tension
of the rope has | \
40 lbs of | \
tension | \
| \
| . Anchor
+----+---+
| 40 lbs |
+--------+

No matter how you do it, in order to support the 40lb load, the sum of
all ropes attached to the load has to add up to 40lbs. If you're using
a simple pulley at the top and attach both ends of the rope to the load,
then the rope has a tension of 20lbs and both sides add up to a total
of 40 lbs. If you instead attach one end of the rope to an anchor, then
the rope has an tension of 40 lbs and the hook at the top is having to
support a total of 80 lbs.

The weight will remain quite nicely right where it is.
What is the pull on the hook?? Where did the 40 lbs go??

I hope you answer this as you do appear to know what you are talking
about. Just don't let what seems logical lead you down stray paths.
Yes, on first glance the original problem appears to need a 80 lb
strain but unfortunately it isn't true in real life. A simple test (or
reference to any physics text) will show you in less than a minute.

Harry K

You didn't show how attaching the rope back to bucket is in anyway
different than attaching to a separate anchor. You are still assuming
a non-existant 40 lb load. It is the same load extended to the anchor
or the bucket handle. The text book I did find did at least -mention-
the force extending through the hook but did not specifically mention
what the force was, i.e., was it 1/2 the load or the whole load.

Harry,
LOOK at the 1st diagram on this posting. The one that shows both ends
of the rope attached to the 40lb load. You'll notice that both ends have
20lbs of tension. Two rope ends at 20lbs each is capable of supporting
a 40lb load.

Now LOOK at the 2nd diagram where one end of the rope is attached to the
load and the other end is attached to an anchor. Now since there is only
one end of the rope attached to the load, that end has to have 40 lbs of
tension in order to support a 40 lb load. The other end of the rope also
has to have 40 lbs of tension in order to keep it from running out of
the pulley.

Now LOOK at the 1st diagram again. Note that the rope is under 20 lbs of
tension. Notice that the rope goes to and from the pulley for 2 force
vectors from the pulley. Each vector has 20 lbs and 2 times 20 is 40.

Once again LOOK at the 2nd diagram. Note that in this diagram the rope is
under 40 lbs of tension. Once again, notice that the rope goes to and from
the pulley for once again 2 force vectors. However, since the force vectors
are now 40lbs instead of 20lbs, the force that the top pulley is having to
support is now 40 times 2 for a total of 80 lbs.

The tension in the rope doubles when going from both attachment points on
the load to a single attachment point on the load and a single attachment
point on an anchor.

Personally, I enjoy teaching someone something and seeing the light bulb
go off when the student realizes what is going on. But, I'll forgo that
pleasure in your case since it seems that the bulb is burnt out.

If you continue to ignore what everyone else in this newsgroup continues to
say, then I can only come to one of three conclusions.

1. You're a idiot.
2. You're a liar.
3. You're a troll.

I really don't care which of the above conclusions is the correct one since
it's obvious that in all three cases the correct thing to do is to drop it
and allow you to kill yourself off (hopefully before you reproduce) by
killing yourself in the future by overloading a hoist due to your massive
ignorance of physics.

Later people.

DON'T FEED THE TROLL

Figuring loads / block & tackle theory
 

Douglas and Rosemarie Miller wrote in message gy.com...
In article ,
says...
(Chris Lewis) wrote in message ...
According to :
Harry K wrote:
Don't bother, he won't believe you but just to prove it -again- I just
re-ran the experiment. Bucket weighed 26 lbs this time


scale reads 26 (taa daa!)
I\
I \
I \
I \
I \
I \
I \
bucket anchor
26 lb

Again he won't believe it and refuses to do the same experiment

You are either lying, or you've tied off the rope to the scale and the
anchor isn't doing anything, or possibly you don't have the scale in the
right place.

Or he anchored it to the bucket...


Hey, good point!. In practice it doesn't matter if the rope is
attached to an anchor or tied back to the bucket. The result is the
same. No forces are changed and the bucket remains in place. Think
about it.

But it *does* matter. The forces *are* changed, and the result is *not*
the same -- as you would know, if you ever conducted the test that you
keep challenging others to do.

The scale will read 52 lbs assuming it's between the hook and the rope,
and the rope is free to slide such that it needs to be tied off.

Right.


Yep, and that is just how I rigged it, scale from hook to rope and I
eased the rope on the scale several times before reading. Try it
yourself. It will only take you a minute.

If you actually conducted the test, rigged as you show in your diagram
above, then you're lying about the reading on the scale.

Here it is again. You are beginning to have me thinking I am wrong but
my tests prove I am right, and no, I am not lying as anyone can re-do
the test in a minute. I was wondering if my scale was perhaps not
reading right as it only goes to 25 lbs and my weight prior were near
that so I decreased the weight.

Test one rope over scale hook back to bucket:
SCALE
I
O
I I
I I
I I
I I
I I
I I
I I
16 Lb weight.

Just bucket = 16 lb
Rope over hook and back to bucket = 16lb

Test 2 - Rope over scale hook angle to anchor and tension eased
several times before reading. Three tries.

SCALE
I
O
I \
I \
I \
I \
I \
I \
I Anchor
16 LB weight

Readings:
bucket scale
18 21
16 21
16 21

I can't explain.
1. Where did the 18 reading come from? Anomalous but there it is and
I reported it.
2. Why 5 lbs more to the anchor? I know the angle changes the force
vector and thus (I assume) the reading some, but I wouldn't think 5
lbs worth. The angle (measured with a bevel gauge and then the saw
angle scale from that is:
40 degree give or take a degree.

While doing that I ran another test. Rope was laying in the water
between times so it was now soaked.

bucket 17 scale 21 to 23 depending on how the rope was eased on the
hook.

Once again the scale is crude but the readings are as I have given
them. Why would I lie? Anyone can repeat the test in a minute or
less.

Harry K

Figuring loads / block & tackle theory
 

Douglas and Rosemarie Miller wrote in message gy.com...
In article ,
says...
(Chris Lewis) wrote in message ...
According to :
Harry K wrote:
Don't bother, he won't believe you but just to prove it -again- I just
re-ran the experiment. Bucket weighed 26 lbs this time


scale reads 26 (taa daa!)
I\
I \
I \
I \
I \
I \
I \
bucket anchor
26 lb

Again he won't believe it and refuses to do the same experiment

You are either lying, or you've tied off the rope to the scale and the
anchor isn't doing anything, or possibly you don't have the scale in the
right place.

Or he anchored it to the bucket...


Hey, good point!. In practice it doesn't matter if the rope is
attached to an anchor or tied back to the bucket. The result is the
same. No forces are changed and the bucket remains in place. Think
about it.

But it *does* matter. The forces *are* changed, and the result is *not*
the same -- as you would know, if you ever conducted the test that you
keep challenging others to do.

The scale will read 52 lbs assuming it's between the hook and the rope,
and the rope is free to slide such that it needs to be tied off.

Right.


Yep, and that is just how I rigged it, scale from hook to rope and I
eased the rope on the scale several times before reading. Try it
yourself. It will only take you a minute.

If you actually conducted the test, rigged as you show in your diagram
above, then you're lying about the reading on the scale.

Douglas and Rosemarie Miller wrote in message gy.com...
In article ,
says...
(Chris Lewis) wrote in message ...
According to :
Harry K wrote:
Don't bother, he won't believe you but just to prove it -again- I just
re-ran the experiment. Bucket weighed 26 lbs this time


scale reads 26 (taa daa!)
I\
I \
I \
I \
I \
I \
I \
bucket anchor
26 lb

Again he won't believe it and refuses to do the same experiment

You are either lying, or you've tied off the rope to the scale and the
anchor isn't doing anything, or possibly you don't have the scale in the
right place.

Or he anchored it to the bucket...


Hey, good point!. In practice it doesn't matter if the rope is
attached to an anchor or tied back to the bucket. The result is the
same. No forces are changed and the bucket remains in place. Think
about it.

But it *does* matter. The forces *are* changed, and the result is *not*
the same -- as you would know, if you ever conducted the test that you
keep challenging others to do.

The scale will read 52 lbs assuming it's between the hook and the rope,
and the rope is free to slide such that it needs to be tied off.

Right.


Yep, and that is just how I rigged it, scale from hook to rope and I
eased the rope on the scale several times before reading. Try it
yourself. It will only take you a minute.

If you actually conducted the test, rigged as you show in your diagram
above, then you're lying about the reading on the scale.

Here it is again. You are beginning to have me thinking I am wrong but
my tests prove I am right, and no, I am not lying as anyone can re-do
the test in a minute. I was wondering if my scale was perhaps not
reading right as it only goes to 25 lbs and my weight prior were near
that so I decreased the weight.

Test one rope over scale hook back to bucket:
SCALE
I
O
I I
I I
I I
I I
I I
I I
I I
16 Lb weight.

Just bucket = 16 lb
Rope over hook and back to bucket = 16lb

Test 2 - Rope over scale hook angle to anchor and tension eased
several times before reading. Three tries.

SCALE
I
O
I \
I \
I \
I \
I \
I \
I Anchor
16 LB weight

Readings:
bucket scale
18 21
16 21
16 21

I can't explain.
1. Where did the 18 reading come from? Anomalous but there it is and
I reported it.
2. Why 5 lbs more to the anchor? I know the angle changes the force
vector and thus (I assume) the reading some, but I wouldn't think 5
lbs worth. The angle (measured with a bevel gauge and then the saw
angle scale from that is:
40 degree give or take a degree.

While doing that I ran another test. Rope was laying in the water
between times so it was now soaked.

bucket 17 scale 21 to 23 depending on how the rope was eased on the
hook.

Once again the scale is crude but the readings are as I have given
them. Why would I lie? Anyone can repeat the test in a minute or
less.

To all the naysayers out there. Do the damn test and be honest about
your results. I am and have been (at least 4 times now). Basically all
you all are doing is sticking your fingers in your ears and repeating
'tis not' rather than taking the time to do a simple test. Doug claims
he has but isn't honest about his readings as I just proved (again).

Harry K

Figuring loads / block & tackle theory
 

"Michael Daly" wrote in message
...
On 16-Mar-2004, (Doug Miller) wrote:

You know that, I know that, Mike knows that

I can't help but notice that he hasn't responded to a single one
of my posts.

Mike

One more round and I give up, admit defeat, and petition ALL science and
engineering books to change as they are all wrong!
Greg

Figuring loads / block & tackle theory
 

In article ,
Harry K wrote:
SNIP...

See your error? You have translated the Class 1 pulley in the problem
into a Class 2 pulley in your example. Just invert your diagram and
you will see that the pulley is attached to your hand and you are in
effect pulling the 40 lb wt 1 foot to lift your hand 2 ft. Class 2
pulley.

Harry,
Let's see if I can eliminate that class 1 vs class 2 pulley bull ****
from your thinking. Let me change the problem on you.

If I understand your definitions correctly, a class 1 pulley is one
that doesn't move and a class 2 pulley is one that moves. Hopefully
the following example will show you that there ISN'T ANY DIFFERENCE
IN THE LOAD BETWEEN A CLASS 1 OR A CLASS 2 PULLEY.....

Force being applied here
^
|
| . Anchor
| /
| /
| /
| /
| /
| /
O
+---------------+--------------+
| Large object that requires |
| 100 lbs of force in order |
| to drag it across the ground |
+------------------------------+

Now I want you to figure out how much force the pulley is providing
to the load in an attempt to drag that load across the ground.

Example 1. You allow 0 lbs of force in an attempt to drag the load.
The pulley is now providing 0 lbs of force against the load
and is stationary. What you call a class 1 pulley.

Example 2. You are now applying 10 lbs of force in an attempt
to drag the load.
The pulley is still stationary (class 1) and is providing 20 lbs
of force against the load.

Example 3. You are now applying 20 lbs of force in an attempt
to drag the load.
The pulley is still stationary (class 1) and is providing 40 lbs
of force against the load.

Example 4. You keep smoothly increasing the force that you apply in an attempt
to move the load. The force the pulley applies smoothly increases
at twice the rate until you finally apply 50 lbs of force which
the pulley translates to 100lbs. At this point there is enough
force available to drag the load and the pulley is what you
call a class 2 pulley.

The above examples are how the situition works in the real world. Now to show
you how things work in the your "world".

In example 1 where 10 lbs of force is being applied to the rope, you'll claim
that since the pulley isn't moving, it is a class 1 pulley and only 10 lbs
of force is being applied by the pulley.

As you continue to smoothly increase the force up to, but not quite 50 lbs.
The pulley will continue to be a class 1 pulley and only apply a force equal
to what you're pulling.

Finally as you reach that magic 50 lb mark, the pulley suddenly transforms
itself into a class 2 pulley and magically doubles the force being applied
to the load to make a force of 100 lbs and move the load.

Which situition makes more sense?

The simpliest method that I can describe to you about how much force is
being applied is for you to count the number of times that the rope goes
to the object and multiply by the tension in the rope. That number will be
the amount of force being applied to the object. Examples:

|
O
| \
| \
| \
| \
|
+----+---+
| 40 lbs |
+--------+

In the above example, I'm assuming that you're simply pulling on the end of
the rope. The rope touches you once and therefore is applying a 40 lb
resistance to you. The rope is touching the load once and is therefore also
applying 40 lbs of force. The kicker is that the rope is touching the pulley
twice (coming and going) and is therefore applying an 80 lb force against it.

Anchor

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
Douglas and Rosemarie Miller wrote in message
gy.com...
In article ,
says...
[big snip]

Someone way up thread posted at link to a site
giving the good explanation.

Once again, Harry, you're caught in a lie. The site posted does *not*
support your position here, despite your false claim that it does.
Here's the relevant part of the post you refer to:

http://www.howstuffworks.com/pulley.htm

This web page speaks to the issue of how much pull is needed on the rope
to make the weight go up. But it does not adress the felt weight on the
pulley hook.

Note that last sentence, Harry: "does not adress [sic] the weight on the
hook".


And just where did I say that it did? I said that someone had posted
a link, you found it. I didn't read it.

You apparently haven't read very much of anything -- including what you
yourself have written. You said that the link was to "a site giving the good
explanation." In fact, that site doesn't explain *anything* that is relevant
to this discussion.

One citation, Harry, just *one*, of a published source that supports your
claims. Just one.

We're waiting.

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
Douglas and Rosemarie Miller wrote in message
gy.com...
In article ,
says...
(Chris Lewis) wrote in message
...
According to :
Harry K wrote:
Don't bother, he won't believe you but just to prove it -again- I
just
re-ran the experiment. Bucket weighed 26 lbs this time


scale reads 26 (taa daa!)
I\
I \
I \
I \
I \
I \
I \
bucket anchor
26 lb

Again he won't believe it and refuses to do the same experiment

You are either lying, or you've tied off the rope to the scale and the
anchor isn't doing anything, or possibly you don't have the scale in
the
right place.

Or he anchored it to the bucket...


Hey, good point!. In practice it doesn't matter if the rope is
attached to an anchor or tied back to the bucket. The result is the
same. No forces are changed and the bucket remains in place. Think
about it.

But it *does* matter. The forces *are* changed, and the result is *not*
the same -- as you would know, if you ever conducted the test that you
keep challenging others to do.

The scale will read 52 lbs assuming it's between the hook and the rope,

and the rope is free to slide such that it needs to be tied off.

Right.


Yep, and that is just how I rigged it, scale from hook to rope and I
eased the rope on the scale several times before reading. Try it
yourself. It will only take you a minute.

If you actually conducted the test, rigged as you show in your diagram
above, then you're lying about the reading on the scale.

Here it is again. You are beginning to have me thinking I am wrong but
my tests prove I am right, and no, I am not lying as anyone can re-do
the test in a minute.

If the tests that you claim to have conducted give the results that you claim
that they do, then you're setting them up wrong *and* describing them wrong
here.

I was wondering if my scale was perhaps not
reading right as it only goes to 25 lbs and my weight prior were near
that so I decreased the weight.

Test one rope over scale hook back to bucket:
SCALE
I
O
I I
I I
I I
I I
I I
I I
I I
16 Lb weight.

Just bucket = 16 lb
Rope over hook and back to bucket = 16lb

OK, look at the forces involved there. You've suspended a 16-lb weight by two
ropes, each of which *clearly* bears 8 lb of the load. And the scale at the
top reads 16 lb -- CORRECTLY showing that the load in BOTH ropes is exerted
against the top support.


Test 2 - Rope over scale hook angle to anchor and tension eased
several times before reading. Three tries.

SCALE
I
O
I \
I \
I \
I \
I \
I \
I Anchor
16 LB weight

Readings:
bucket scale
18 21
16 21
16 21

The readings you report are not consistent with your diagram, which shows only
one scale at the top. You purport to have made two force measurements with
only one scale. Nice trick.


I can't explain.
1. Where did the 18 reading come from? Anomalous but there it is and
I reported it.

Operator error.

2. Why 5 lbs more to the anchor? I know the angle changes the force
vector and thus (I assume) the reading some, but I wouldn't think 5
lbs worth. The angle (measured with a bevel gauge and then the saw
angle scale from that is:
40 degree give or take a degree.

Where are you taking this measurement? According to your diagram, you had a
*single* scale at the top. What does *that* scale show?

While doing that I ran another test. Rope was laying in the water
between times so it was now soaked.

bucket 17 scale 21 to 23 depending on how the rope was eased on the
hook.

What does the scale _at_the_top_ show, Harry? That's what we're arguing about.
Nobody cares what the load is in the individual ropes. What's the load at the
top?

Once again the scale is crude but the readings are as I have given
them. Why would I lie? Anyone can repeat the test in a minute or
less.

Then I suggest you do the test: arrange the weight, scale, and anchor as shown
in your diagram above and reproduced he

SCALE
I
O
I \
I \
I \
I \
I \
I \
I Anchor
16 LB weight

and report what the scale at the top reads.

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
[snip]
Test 2 - Rope over scale hook angle to anchor and tension eased
several times before reading. Three tries.

SCALE
I
O
I \
I \
I \
I \
I \
I \
I Anchor
16 LB weight

Readings:
bucket scale
18 21
16 21
16 21

[snip]

To all the naysayers out there. Do the damn test and be honest about
your results.

To you, Harry, I say: do the damn test and be honest about your results. Set
it up like you show in that diagram above and report what the scale
_at_the_top_ reads. Not the readings in the individual ropes. We're not
talking about the loads in the individual ropes. That's completely irrelevant.
The *only* point under discussion is the load _at_the_top.

I am and have been (at least 4 times now). Basically all
you all are doing is sticking your fingers in your ears and repeating
'tis not' rather than taking the time to do a simple test. Doug claims
he has but isn't honest about his readings as I just proved (again).

You have proved nothing except your own lack of understanding. The only thing
that matters is the weight _at_the_top.

I've been completely honest about my readings, Harry. Look at the post in
which I described my second test, for example. If I were making up the
readings, why would I report something that differed from theory by 20%?

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
Douglas and Rosemarie Miller wrote in message
gy.com...
In article ,
says...
(Chris Lewis) wrote in message
...
According to :
Harry K wrote:
Don't bother, he won't believe you but just to prove it -again- I
just
re-ran the experiment. Bucket weighed 26 lbs this time


scale reads 26 (taa daa!)
I\
I \
I \
I \
I \
I \
I \
bucket anchor
26 lb
[major snippage]

Why would I lie? Anyone can repeat the test in a minute or
less.

Why would you lie? I don't know. I'm not a psychologist. But I do know this:
in the "experiment" shown above, you're lying about *something*. Or describing
your experiment inaccurately, if you prefer that phrasing. Set up as you claim
to have set it up, it simply does not give the readings that you claim it
gives.

Figuring loads / block & tackle theory
 

"Greg O" wrote in message ...
"Michael Daly" wrote in message
...
On 16-Mar-2004, (Doug Miller) wrote:

You know that, I know that, Mike knows that

I can't help but notice that he hasn't responded to a single one
of my posts.

Mike

One more round and I give up, admit defeat, and petition ALL science and
engineering books to change as they are all wrong!
Greg

http://science.howstuffworks.com/pulley.htm

Best I could find on the net. Do you see the force vector arrows in
the diagram? They show 100 lbs down force on the right, 100 lbs up
force on the right and another 100 lbs down force on the left. Notice
the two 100 lbs down? Yep, that would mean 200 lbs on the hook.
But wait a minute. There is one 100 lbs -up- force. That cancels one
of the downs leaving

100 lbs remaining acting on the weight and the hook.

How about discussing my tests and the results (not just claiming I am
lying) or even better take minute and do the test yourself.

Logic doesn't always work. Here is one example:

Two cars of equal mass, both going 50 mph crash head on. Car 1 feels
a crash equal to 100 mph.

Harry K

Figuring loads / block & tackle theory
 

"Greg O" wrote in message ...
"Michael Daly" wrote in message
...
On 16-Mar-2004, (Doug Miller) wrote:

You know that, I know that, Mike knows that

I can't help but notice that he hasn't responded to a single one
of my posts.

Mike

Mike, I apologize if I missed you but I don't see any in my google
reader. I just reviewed the entire list of posts and still don't see
any. If you have a point that hasn't been raised try again or put it
to one of Greg or Doug's. The only points that have been raised by
any of them all come down to -you are wrong, you are lying- and the
like. None have posted any research, only one claims to have done the
test and he lied about the results. See my other post to Greg for a
cite. I am still looking for a better one but not holding any hopes.

Harry K

Figuring loads / block & tackle theory
 

(Doug Miller) wrote in message gy.com...
In article , (Harry K) wrote:

snip a batch of bs that still comes down to simple -I don't believe
it, you are lying, you didn't do the tests etc-.

With all your prattling about physics books, I would have thought that you had
one already. Convenient for you that you don't.

One cite, Harry, just one cite, of a published work that supports your claims.
Where is it?

Let's see, I have posted at least 4 different tests, all agree with my
assertion (and physics) and you have done what? Claimed to have done
1 test and then lied about the result if you even did it.

Post a picture of your test and result. Post some research, Post
anything at all except 'I don't believe it'.

How about actually discuss one or more of my readings. Something more
than
that's wrong. Show how it is wrong. Just stating that it doesn't
agree with your preconceived idea isn't enough.

Sorry for you. Here is the only one I found that comes close. It is
some better than Tom's. Note that I have done the research, you
haven't.

http://science.howstuffworks.com/pulley.htm

Best I could find on the net. Do you see the force vector arrows in
the diagram? They show 100 lbs down force on the right, 100 lbs up
force on the right and another 100 lbs down force on the left. Notice
the two 100 lbs down? Yep, that would mean 200 lbs on the hook.

But wait a minute. There is one 100 lbs -up- force. That cancels one
of the downs leaving

100 lbs remaining acting on the weight and the hook. Just as I said
and just as my tests show.

Of course I now expect you to reply 'that's wrong'

Harry K

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
"Greg O" wrote in message
...
"Michael Daly" wrote in message
...
On 16-Mar-2004, (Doug Miller) wrote:

You know that, I know that, Mike knows that

I can't help but notice that he hasn't responded to a single one
of my posts.

Mike

One more round and I give up, admit defeat, and petition ALL science and
engineering books to change as they are all wrong!
Greg

http://science.howstuffworks.com/pulley.htm

Best I could find on the net. Do you see the force vector arrows in
the diagram? They show 100 lbs down force on the right, 100 lbs up
force on the right and another 100 lbs down force on the left. Notice
the two 100 lbs down? Yep, that would mean 200 lbs on the hook.
But wait a minute. There is one 100 lbs -up- force. That cancels one
of the downs leaving

No, it doesn't.

100 lbs remaining acting on the weight and the hook.

How about discussing my tests and the results (not just claiming I am
lying) or even better take minute and do the test yourself.

I've discussed your purported results ad nauseum, every time you've posted
them. And what you have posted is inconsistent at best, false at worst. For
example, in your latest report of your alleged results, you purport to have
force readings in each leg of the rope but your diagram shows only one scale.
That _can't_ be true. It isn't possible to take readings in two places with
one device. Either your diagram is wrong, or your numbers are wrong.

It's so easy to do this test, I can't imagine why you haven't done it yet.

Logic doesn't always work. Here is one example:

Two cars of equal mass, both going 50 mph crash head on. Car 1 feels
a crash equal to 100 mph.

Absolutely false. You clearly understand nothing of physics.

Each vehicle decelerates in the same time and distance as it would have, had
it collided with a fixed object at 50 mph.

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
"Greg O" wrote in message
...
"Michael Daly" wrote in message
...
On 16-Mar-2004, (Doug Miller) wrote:

You know that, I know that, Mike knows that

I can't help but notice that he hasn't responded to a single one
of my posts.

Mike

Mike, I apologize if I missed you but I don't see any in my google
reader. I just reviewed the entire list of posts and still don't see
any. If you have a point that hasn't been raised try again or put it
to one of Greg or Doug's. The only points that have been raised by
any of them all come down to -you are wrong, you are lying- and the
like. None have posted any research, only one claims to have done the
test and he lied about the results.

No, Harry, it is _you_ who is lying about results. Or about your test setups.
One or the other. The setups you purport to be measuring simply don't give the
results you report.

We're still waiting for the photos of your setups, Harry.

See my other post to Greg for a
cite. I am still looking for a better one but not holding any hopes.

That cite does *not* in any fashion support your claims.

Figuring loads / block & tackle theory
 

In article , (Harry K) wrote:
(Doug Miller) wrote in message
gy.com...
In article ,
(Harry K) wrote:

snip a batch of bs that still comes down to simple -I don't believe
it, you are lying, you didn't do the tests etc-.

With all your prattling about physics books, I would have thought that you
had
one already. Convenient for you that you don't.

One cite, Harry, just one cite, of a published work that supports your
claims.
Where is it?

Let's see, I have posted at least 4 different tests, all agree with my
assertion (and physics) and you have done what? Claimed to have done
1 test and then lied about the result if you even did it.

Posted four different lies, you mean. How about addressing the points that
I've raised in response to your claimed test results -- like how you managed
to get two force measurements while using one scale?

Post a picture of your test and result. Post some research, Post
anything at all except 'I don't believe it'.

Harry, you have repeatedly said that "any physics book" will support your
claims. So find one. We're waiting for the cite.

I've actually done the test, and reported the results that I actually
measured. You either (a) have not done any tests, (b) have lied about your
test setups, or (c) lied about your test results.

Do this test, Harry:

O
|
scale
|
|
O
| \
| \
| \
| \
| \
| \
| \
20# fixed anchor

and report what you read on the scale. That's essentially the same diagram
that you posted a few hours ago, along with what you purported to be readings
in the individual segments of the rope (magically taken in two different
places with a single scale). The readings in the individual segments are
irrelevant, Harry.

What does the scale read _at_the_top? I've asked you that a couple of times
already. Why are you afraid to answer that?



How about actually discuss one or more of my readings. Something more
than
that's wrong. Show how it is wrong. Just stating that it doesn't
agree with your preconceived idea isn't enough.

Sorry for you. Here is the only one I found that comes close. It is
some better than Tom's. Note that I have done the research, you
haven't.

http://science.howstuffworks.com/pulley.htm

Best I could find on the net. Do you see the force vector arrows in
the diagram? They show 100 lbs down force on the right, 100 lbs up
force on the right and another 100 lbs down force on the left. Notice
the two 100 lbs down? Yep, that would mean 200 lbs on the hook.

But wait a minute. There is one 100 lbs -up- force. That cancels one
of the downs leaving

100 lbs remaining acting on the weight and the hook. Just as I said
and just as my tests show.

Of course I now expect you to reply 'that's wrong'

Harry K

Figuring loads / block & tackle theory
 

Doug Miller wrote:

Big snip


Then I suggest you do the test: arrange the weight, scale, and anchor as shown
in your diagram above and reproduced he


SCALE
I
O
I \
I \
I \
I \
I \
I \
I Anchor
16 LB weight


and report what the scale at the top reads.

Actually, you want the anchor as close as possible to the weight, not
off at an angle. When it's some distance from the weight, depending on
how the scale is attached to the ceiling (free to pivot or rigidly
fixed), the scale will also measure some portion of the horizontal
component of the rope's tension and increase its reading, something
everyone has missed so far. (I know it won't make a 2:1 difference.)

BTW, some of you referred to the How Stuff Works link,
http://www.howstuffworks.com/pulley.htm, for supposedly an authorative
explanation of pulleys (even though it doesn't address the issue here).
I see their third figure, the one with one pulley at the weight and the
other at the ceiling, as wrong. At the weight, the rope changes angle
about 60 degrees; that is, each is about 30 degrees from the vertical.
The vertical component of "each" rope's tension must be 50 pounds.
Therefore, the tension in the rope must be 50/cosine 30 = 50/.866 = 57.5
pounds.

Lesson: Don't trust even fancy websites to get simple basics right.

Figuring loads / block & tackle theory
 

[On Wed, 17 Mar 2004 15:18:33 GMT, "Ray K."
wrote:]

Actually, you want the anchor as close as possible to the weight, not
off at an angle. When it's some distance from the weight, depending on
how the scale is attached to the ceiling (free to pivot or rigidly
fixed), the scale will also measure some portion of the horizontal
component of the rope's tension and increase its reading, something
everyone has missed so far. (I know it won't make a 2:1 difference.)

Interesting.

This seems to contradict what Michael (who seems to know
what he is talking about) said about the angle of the rope
from the hook/pulley to the cleat.

Unless I misunderstood, the more vertically down the rope
goes once it leaves the hook, the greater the load on the
hook. Alternatively, the more vertically up the rope
goes, the less the load on the hook.

It all depends on the angle of the dangle, so to speak.

I *think* I am somewhat beginning to understand this. At
least I did before reading the above.

The way I am getting it is that the way to compute things
is to first figure the load on each segment of the rope,
then to back off and look at the overall operation. Add
the loads on all the rope segments and see where the total
of them goes.

If the rope is anchored straight back down to the same
pot/bucket, then the load on the rope segments would
divide in half -- 20 pounds on each side. That would
place a total of 40 pounds on the hook.

If the rope is anchored vertically down to a separate
cleat, then each side of the rope would be bearing the
full 40 pounds. That would place 40x2=80 on the hook.

You seem to disagree with this.

(The trig portion of the problem goes way over my head. I
may need to take a class at the local community college.)

--
Harry

Figuring loads / block & tackle theory
 

In article , "Ray K." wrote:
Doug Miller wrote:

Big snip


Then I suggest you do the test: arrange the weight, scale, and anchor as
shown
in your diagram above and reproduced he


SCALE
I
O
I \
I \
I \
I \
I \
I \
I Anchor
16 LB weight


and report what the scale at the top reads.

Note that we're still waiting for Harry to respond to this...

Actually, you want the anchor as close as possible to the weight, not
off at an angle. When it's some distance from the weight, depending on
how the scale is attached to the ceiling (free to pivot or rigidly
fixed), the scale will also measure some portion of the horizontal
component of the rope's tension and increase its reading, something
everyone has missed so far. (I know it won't make a 2:1 difference.)

Actually, that's been addressed by at least one of, and I think both, Michael
Daly and John Cochran earlier in this thread.

BTW, some of you referred to the How Stuff Works link,
http://www.howstuffworks.com/pulley.htm, for supposedly an authorative
explanation of pulleys (even though it doesn't address the issue here).
I see their third figure, the one with one pulley at the weight and the
other at the ceiling, as wrong. At the weight, the rope changes angle
about 60 degrees; that is, each is about 30 degrees from the vertical.
The vertical component of "each" rope's tension must be 50 pounds.
Therefore, the tension in the rope must be 50/cosine 30 = 50/.866 = 57.5
pounds.

Lesson: Don't trust even fancy websites to get simple basics right.

Figuring loads / block & tackle theory
 

In article , (The Other Harry) wrote:
[On Wed, 17 Mar 2004 15:18:33 GMT, "Ray K."
wrote:]

Actually, you want the anchor as close as possible to the weight, not
off at an angle. When it's some distance from the weight, depending on
how the scale is attached to the ceiling (free to pivot or rigidly
fixed), the scale will also measure some portion of the horizontal
component of the rope's tension and increase its reading, something
everyone has missed so far. (I know it won't make a 2:1 difference.)

Interesting.

This seems to contradict what Michael (who seems to know
what he is talking about) said about the angle of the rope
from the hook/pulley to the cleat.

It's not relevant to the larger question of whether the load on the hook is
equal to the weight of the suspended mass, or (approximately) double that.

Unless I misunderstood, the more vertically down the rope
goes once it leaves the hook, the greater the load on the
hook. Alternatively, the more vertically up the rope
goes, the less the load on the hook.

Permit me to restate for clarity: The closer the anchored segment of the rope
is to vertical, the greater the load on the hook. Alternatively, the closer
that segment is to horizontal, the less the load on the hook.

It all depends on the angle of the dangle, so to speak.

I *think* I am somewhat beginning to understand this. At
least I did before reading the above.

The way I am getting it is that the way to compute things
is to first figure the load on each segment of the rope,
then to back off and look at the overall operation. Add
the loads on all the rope segments and see where the total
of them goes.

Correct.

If the rope is anchored straight back down to the same
pot/bucket, then the load on the rope segments would
divide in half -- 20 pounds on each side. That would
place a total of 40 pounds on the hook.

Correct.

If the rope is anchored vertically down to a separate
cleat, then each side of the rope would be bearing the
full 40 pounds. That would place 40x2=80 on the hook.

Correct.

You seem to disagree with this.

He's not disagreeing with it, just refining the analysis of the problem.
Unnecessarily so IMHO as it tends to cloud the issue, but that's just MHO.

(The trig portion of the problem goes way over my head. I
may need to take a class at the local community college.)

Although trig makes the analysis a bit easier, it's not required. The analysis
can be done entirely by geometric and algebraic methods. Consider a force
being exerted at an angle from the vertical ('f' in the diagram below):

|\
| \
| \
v | \ f
| \
| \
|___\
h

This is a right triangle, and thus obeys the Pythagorean Theorem:
f x f = ( h x h ) + (v x v )

The individual vertical and horizontal components of the force f are
proportional to the vertical and horizontal components of the distance. For
example, if f represents a force of 10 pounds acting along a distance of 5
feet, and the distance at v is measured at 4 feet, then the distance h is
calculated to be 3 feet: 5 x 5 = ( 4 x 4 ) + ( 3 x 3 ). The vertical and
horizontal components of the force are 8 and 6 pounds respectively.

Figuring loads / block & tackle theory
 

In article ,
(Harry K) wrote:
[snip]
Logic doesn't always work. Here is one example:

Two cars of equal mass, both going 50 mph crash head on. Car 1 feels
a crash equal to 100 mph.

Proving, once again, your absolute ignorance of physics. The following is
excerpted from http://www.unmuseum.org/soearch/over0104.htm (about 1/3 of the
way down). Note in particular the third paragraph of the reply to the
question.

[begin quote]

The Wall or the Car?

In her book "Brain Building" Marilyn Vos Savant says that when two cars
collide head on, with each car traveling at 50 MPH, the effect on each car is
the same as if it had hit a stone wall at 50 MPH. I can't believe this. It
seems to me the effect should be that of a 100 MPH collision
- Thomas

This is a longtime favorite of physics teachers and it has two answers. In the
"ideal" situation that Ms. Savant is talking about each of the cars has a
certain amount of kinetic energy as they move (let's call this value E). If
they cars are identical in every way (speed, mass, shape) and they do a
perfect head-on collision the total energy involved will be 2 times E or 2E.
Since there are two cars the energy will be divided in half and each one will
be subjected to one E of kinetic energy which will deform the vehicles
turning them into something that looks like a two-ton metal accordion.

If we are dealing with one car hitting a wall then we will have one E of
kinetic energy before the accident (The wall has no energy, it's not moving).
If the wall is absolutely rigid and does not absorb any of the energy of the
impact then again there will be one E of energy to deform one car.

This is why safety crash tests simulating head-on collisions are done by
launching a car into a rigid barrier. It is a good simulation of a head-on
collision, but only requires one vehicle.

If this seem unintuitive try it at home (not with cars, use tennis balls).
Roll them at each other and when they hit note how far do they bounce back.
Now roll one at the same speed toward a immovable object (like a brick). Did
it bounce back the same distance? It should have it you gave it the same
initial speed.

The second solution involves what happens in a non-ideal situation. Very
rarely in the real world would a car hit a totally immovable barrier. If the
barrier absorbed some of the energy less would left over to damage the car.
Also if two cars hit it is unlikely that they would be identical in speed and
shape or be aligned perfectly head on. They would tend to bounce off each
other and penetrate each other as well as spin off at an angle and these
actions would absorb energy. For these reasons in it would be hard to say
which accident would result in more damage to the car in a real life
situation.

[end quote]

Figuring loads / block & tackle theory
 

Harry K wrote:
snip Harry's trying to claim he isn't lying about his test

Sorry for you. Here is the only one I found that comes close. It is
some better than Tom's. Note that I have done the research, you
haven't.

http://science.howstuffworks.com/pulley.htm

Best I could find on the net. Do you see the force vector arrows in
the diagram? They show 100 lbs down force on the right, 100 lbs up
force on the right and another 100 lbs down force on the left. Notice
the two 100 lbs down? Yep, that would mean 200 lbs on the hook.

But wait a minute. There is one 100 lbs -up- force. That cancels one
of the downs leaving

Count all the forces Harry. There's _three_ 100 lb down forces, and one
100 lb up force. That's two hundred pounds down, not that you care.

But thier diagram is fubar.

100 lbs remaining acting on the weight and the hook. Just as I said
and just as my tests show.

Well, just to humor the net kook, I did the test. As I expected the load
is twice as high as the weight.

Now, let's try a more novel approach that may get through to you.

With this set up:

|
+
/|\
| |
|\_/|
| |
| |
A B

Even you will agree that load A must equal load B if the pully is to
remain in balance. Also, you'l not that for every inch you move B down, A
will go up one inch. If you read your cite you'll see the force-distance
trade off. Essentially if the distances moved are one to one, then the
loads are one to one. If, as in the second picture on the how stuff works
site, the pullys are arranged such that the load moves only half the
distance the rope is pulled, then the pull on the rope must also be half
the load. Agreed?


OK, now. The A-B pully I diagramed above is also a scale of sorts. We
know that A must equal B.

Now, let's take B and attach another pully arangement just like the one
we've used befo

|
+
/|\
| |
|\_/|
| |
| |
A B
|
+
/|\
| |
|\_/|
| |
| |
C D

Pully CD is now the same set up with the planter. The load at B is the
load we've been discussing. The load at A will be the answer. OK, now, D
is fixed: tied off to the ground. We move C down one inch.

Q1: How far does B move?
A1: it moves down one half inch.

Q2: How far does A move then?
A2: it moves up one half inch.

Q3: What is the ratio of distances moved from C to A?
A3: Two to One.

Since we've established that the ratio of distances moved governs the
ratio of the loads, then it must be that the load at A equals twice the
load at C. Since the load at B must equal the load at A we get the load
at B equal to twice the load at C.

Just like everyone has been trying to tell you.



John
--
Remove the dead poet to e-mail, tho CC'd posts are unwelcome.
Ask me about joining the NRA.

Figuring loads / block & tackle theory
 

Doug Miller wrote:

Actually, you want the anchor as close as possible to the weight, not
off at an angle. When it's some distance from the weight, depending on
how the scale is attached to the ceiling (free to pivot or rigidly
fixed), the scale will also measure some portion of the horizontal
component of the rope's tension and increase its reading, something
everyone has missed so far. (I know it won't make a 2:1 difference.)


Actually, that's been addressed by at least one of, and I think both, Michael
Daly and John Cochran earlier in this thread.

Sorry, I must have missed those posts.

Ray

Figuring loads / block & tackle theory
 

Figuring loads / block & tackle theory
 

Figuring loads / block & tackle theory
 

(Doug Miller) wrote in message gy.com...
In article , (Harry K) wrote:
"Greg O" wrote in message
...
"Michael Daly" wrote in message
...
On 16-Mar-2004, (Doug Miller) wrote:

You know that, I know that, Mike knows that

I can't help but notice that he hasn't responded to a single one
of my posts.

Mike

One more round and I give up, admit defeat, and petition ALL science and
engineering books to change as they are all wrong!
Greg

http://science.howstuffworks.com/pulley.htm

Best I could find on the net. Do you see the force vector arrows in
the diagram? They show 100 lbs down force on the right, 100 lbs up
force on the right and another 100 lbs down force on the left. Notice
the two 100 lbs down? Yep, that would mean 200 lbs on the hook.
But wait a minute. There is one 100 lbs -up- force. That cancels one
of the downs leaving

No, it doesn't.

100 lbs remaining acting on the weight and the hook.


Just as I predicted. Your answer is 'that is wrong". Argue with the
site I cited, not me. It proves you wrong.

How about discussing my tests and the results (not just claiming I am
lying) or even better take minute and do the test yourself.

I've discussed your purported results ad nauseum, every time you've posted
them. And what you have posted is inconsistent at best, false at worst. For
example, in your latest report of your alleged results, you purport to have
force readings in each leg of the rope but your diagram shows only one scale.
That _can't_ be true. It isn't possible to take readings in two places with
one device. Either your diagram is wrong, or your numbers are wrong.

O.K. over to you. Show *any* place in that post where I even *refer*
to forces on *any* leg of the rope. In fact show anywhere where I
posted a reading other than from the scale at the top. Good luck.


It's so easy to do this test, I can't imagine why you haven't done it yet.

Logic doesn't always work. Here is one example:

Two cars of equal mass, both going 50 mph crash head on. Car 1 feels
a crash equal to 100 mph.

Absolutely false. You clearly understand nothing of physics.

Each vehicle decelerates in the same time and distance as it would have, had
it collided with a fixed object at 50 mph.

Hey you got it. You would be amazed at how many people don't and
refuse to believe it even when clearly explained as you have done.

Here is another one. My brother has 2 children, one is a girl. What
are the odds the 2nd is a girl?

I have now performed many experiments, listed honest results, given
you a citation showing the force vectors and all you have done is run
your mouth saying I am lying and the one citation is wrong.

End of discussion. You have proved that you can lead a horse to water
but you can't make hime drink. Enjoy your ignorance.

Bye.

Harry K

Figuring loads / block & tackle theory
 

Figuring loads / block & tackle theory
 

(Doug Miller) wrote in message gy.com...
In article , (Harry K) wrote:
Douglas and Rosemarie Miller wrote in message
gy.com...
In article ,
says...
[big snip]

Someone way up thread posted at link to a site
giving the good explanation.

Once again, Harry, you're caught in a lie. The site posted does *not*
support your position here, despite your false claim that it does.
Here's the relevant part of the post you refer to:

http://www.howstuffworks.com/pulley.htm

This web page speaks to the issue of how much pull is needed on the rope
to make the weight go up. But it does not adress the felt weight on the
pulley hook.

Note that last sentence, Harry: "does not adress [sic] the weight on the
hook".


And just where did I say that it did? I said that someone had posted
a link, you found it. I didn't read it.

You apparently haven't read very much of anything -- including what you
yourself have written. You said that the link was to "a site giving the good
explanation." In fact, that site doesn't explain *anything* that is relevant
to this discussion.

One citation, Harry, just *one*, of a published source that supports your
claims. Just one.

We're waiting.

See below. I gave a cite and jsut as I predicted you said it was wrong.

Harry K