Finding the Force Exerted on a Log Using Virtual Work Calculations

[balogun]

Virtual work (fireplace thong)

Homework Statement

http://s2.photobucket.com/albums/y31/bambidurojay/?action=view&current=fireplacetong.jpg

I have been given a fireplace thong and need to determine the force exerted on a log.

Homework Equations

It is in the virtual work chapter of my textbook but I cannot see how the equations they have given me relate to the question.

The Attempt at a Solution

see above

 

[mgb_phys]

Think of it as a series of levers ( like individual see-saw or teeter-totter )

ps I think you mean 'tong', fireplace thong sounds very painful.

 

[balogun]

Still can't see how the equation U=intg[F costeta ds] or U=int[M dteta] apply to situation.
help appreciated please.

 

[Astronuc]

One has to work with moments (applied force and moment arm). F is applied about A and induces a moment (force) at C. C then applies a moment about D at N.

There are angles involved, since F is applied at some angle with respect to the moment arm (FA). And the force at C (from the moment with respect to AC) acts at an angle with respect to the moment arm CD.

Statically the moments induced by FB must be equal and opposite FA.

 

[balogun]

Didnt really understand your explanation but i was just playing around with the numbers and seem to have got the anwser

24/17 x17/17 x 17/6=N=4F

thats the right anwser but stiil don't understand it.