Question

What quantity describes the ability of a force to rotate an object? How does it differ from a force? On what quantities does it depend?

Answer 1

Torque -- which depends on applied force, length of lever arm, and the angle between force and lever arm.

Explanation:

Torque is the measure of the ability of a twist to give a body angular acceleration. The formula for torque, `vectau`, is

`vectau = vecr xx vecF`

where `vecr` is the length and direction of the lever arm, and `vecF` is the applied force. All 3 quantities are vectors and the `xx` indicates that a "vector cross product" operation is to be performed. Therefore the magnitude of the torque will be

`|tau| = |r|*|F|*sintheta`

where `theta` is the angle (measured such that it is less than `180^@`) between `vecr and vecF`.

I hope this helps,
Steve