Problem 1

A block is released from rest on a plane inclined at

\theta=30^\circ

. The kinetic-friction coefficient is

\mu_k=0.20

and

g=9.8\,\mathrm{m/s^2}

. Contact is maintained and friction opposes sliding; take the positive axis down the plane. (a) Find the first requested quantity. (b) Find the second quantity. (c) Determine the final result and check its units. (a) Find the normal reaction. (b) Find the kinetic-friction force. (c) Find the acceleration and determine its direction.

problems.proof.stepOf

problems.proof.prevStep problems.proof.nextStep

ma=mg\sin\theta-f_k

problems.proof.analysis

Rearranging the governing relation isolates the first requested result. Keeping the signs explicit also checks that its direction and magnitude are physically sensible.