(John Cochran) wrote in message ...
In article ,
Harry K wrote:
"Stormin Mormon" wrote in message ...
Y'know, that sure sounds reasonable. I don't have a fisherman's spring
scale, but your answer sure sounds reasonable.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


"Greg O" wrote in message
...

"Stormin Mormon" wrote in message
...
Hey, mike, you're confusing the issue! If you have 500 pounds hanging on a
block and tackle, it doesn't matter how many ropes, the screwhook at top
is
still holding 500 pounds (and now I'm confusing the issue).

--


Stormy, you have proven again, without a doubt that you do not know what you
are talking about!
In a situation I described, the hook in the ceiling will feel 2 times the
weight of the flower pot. If you use a more complex block and tackle, one
with several pulleys top and bottem, the more wraps and pulleys you use the
lower the load on the hook in the ceiling, but it will never be less than
the weight of the flower pot, plus the weight of the block and tackle and
the force needed on the rope to suspend the object.

The only way to have less load on the hook than the object weighs is to use
a pulley and the flower pot, and two hooks on the ceiling. then each hook
will hold 1/2 the weight.

If anyone fails to understand this, do as another poster did and get a fish
scale, a pulley, a weight, and a pice of rope, and try it your self!

Well stormin, don't bother to try it as Greg won't believe the
readings anyhow.
And take note that Greg refuses to do the experiment.


Think of ot this way, the pot weighs 40 lbs. If you had a pot hanging on a
length of rope hooked to the ceiling, the rope, hook and all feel a load of
40 lbs. If you add pulley at the ceiling and run the rope over it and back
down, you need to apply a force of 40 lbs to suspend the pot, any more or
less force applied and the pot will go up or down. Now you have TWO 40 lb
loads, the pot, and the force to ballance the weight of the pot, which will
be equal. In this case 40 lbs X 2 = 80 lbs.


You just failed the test again. You don't have two 40 lb loads, you
have one extended over two anchors.


Another way is to think of this whole rope and flower pot situation as a
tetter-totter. You have a 40 lb kid on one side, so you need a 40 lb kid on
the other side to balance it. The weight the fulcrum of the tetter-totter
feels is 80 lbs. Asssuming the tetter-totter weighs nothing.


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

One 40 lb kid is the flower pot, the other 40 lb kid is the force on other
end of the rope needed to suspend the pot, and the fulcrum is the pulley or
hook.

Tomorrow night we will discuss complex block and tackles, test at 10 PM!!
;-)
Greg

Teh best you can hope for is an F

Harry K

Harry,

Here is a little test that you can do that will show you what is going on
and if your scale is inaccurate, the magnitude of the test will still show
you what is going on.

1. Get a 100 lb weight and tie a rope to it.
2. Pass this rope through a pulley.
3. Climb a step ladder holding said pulley.
4. Have a friend pull on the rope to lift the weight.

I'm fairly certain that you a a strong fellow and should have no problems
what-so-ever supporting a measly 100lb load while on the ladder. But I suspect
that you might have a bit of difficultly with a 200lb load.

BTW, I performed the experiment in high school science lab. The load on the
top pulley is twice the load being lifted.

Sorry but it isn't as my simple test that anyone can do in a minute
proves otherwise. If you did it in HS lab and got 2x the load you
failed the experiment. Someone way up thread posted at link to a site
giving the good explanation.

Harry K