View Single Post
  #19   Report Post  
Doug Miller
 
Posts: n/a
Default Figuring loads / block & tackle theory

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

(The Other Harry) wrote:
[On Wed, 10 Mar 2004 14:08:41 GMT, "Michael Daly"
wrote:]

If you don't beleive it, get a spring balance and test it.
You can use a light rope and something weighing only 10lb
or so.

I might just do that.


You'll be surprised. I was -- when I read the first post this morning that
stated it would be 80 lbs, my first thought was "what a bunch of crap". But
the poster's reasoning seemed valid to me. So I tried it, using a reasonably
good spring balance, a toolbox, and a rope. The toolbox, just hanging from

the
spring balance, weighed 28 lbs. Then I tied the rope to the toolbox handle,
passed it through the hook on the balance, stood on one end of the rope, and
lifted the toolbox by the balance: 55 lbs.


I suspect your 55 lb reading was while lifting thus getting friction
force added to the weight. Let it all come to rest and you will be
seeing 28 lbs (plus weight of rope from spring hood to the load).


Nope. 55 while lifting, and about 53 at rest.