# HELP: Equilibrium & Torque

1. Dec 10, 2004

### buffgilville

1) Give the conditions for the equilibrium of an extended object.
An extended object is at equilibrium when no force is acting on it.

2) A uniform ladder of length 6.0m and mass 12.0kg is placed against a smooth vertical wall. The ground is rough.

a) Calculate the force on the ladder from the wall.
vertical forces = 0 = N1 - W
so N1 = 117.72
horizontal forces = 0 = F - N2
Total Torque = 0
0 = F(0) + N1(0) + (12*9.81*cos60*(6/2)) - (N2sin60(6))
so, N2 = 33.98 Newtons

b) Find the minimum coefficient of friction of the ground.
F - 33.98 = 0 ---> F=33.98
friction > F1/N1
so, coefficient of friction=33.98/117.72 ----> 0.289

Are my answers correct? If not, what did I do wrong. Please help. Thanks!

Last edited: Dec 10, 2004
2. Dec 10, 2004

### dextercioby

I'm not going over your problem,but my guess is that:
An extended object is at equilibrium when the resulting momentum of all forces acting on it is nil and the result of all forces acting on it is nil.
It's placing a zero at the left of the dynamics' second law for the rotation movement and for the translation one.

Last edited: Dec 10, 2004
3. Dec 10, 2004

### buffgilville

What's nil ?

4. Dec 10, 2004

### dextercioby

ZERO,NAUGHT,NOTHING,ZIP,LOVE ?????????????
Don't u like football??

5. Dec 11, 2004

### buffgilville

Can someone help me check my work on the other problems, and tell me if they are correct?