Chapter 6, Problem 17P

In Fig. 6-24, a force $\stackrel{\to }{P}$ acts on a block weighing 45 N. The block is initially at rest on a plane inclined at angle θ − 15° to the horizontal. The positive direction of the x axis is up the plane. Between block and plane, the coefficient of static friction is µ_s = 0.50 and the coefficient of kinetic friction is µ_k = 0.34. In unit-vector notation, what is the frictional force on the block from the plane when $\stackrel{\to }{P}$ is (a) (−5.0 N) $\hat{i}$, (b) (−8.0 N) $\hat{i}$, and (c) (−15 N) $\hat{i}$?

Figure 6-24 Problem 17.