# Physics...Friction

posted by
**Christy** on
.

A 75 kg box slides down a 25 degree ramp with an acc. of 3.6 m/s2. find mu,k between the box and the ramp.

Write down Newton's second law for the direction of motion. "a" is the acceleration.

Mg sin 25 - M g cos 25 *mu,k = M a

The first term is the weight component along the direction of motion and the second term is the friction force.

M cancels out. Solve for a.