Chapter 6, Problem 16P

A loaded penguin sled weighing 80 N rests on a plane inclined at angle θ = 20° to the horizontal (Fig. 6-23). Between the sled and the plane, the coefficient of static friction is 0.25, and the coefficient of kinetic friction is 0.15. (a) What is the least magnitude of the force $\stackrel{\to }{F}$, parallel to the plane, that will prevent the sled from slipping down the plane? (b) What is the minimum magnitude F that will start the sled moving up the plane? (c) What value of F is required to move the sled up the plane at constant velocity?

Figure 6-23 Problems 16 and 22.