Halliday, Resnick & Walker — Force and Motion–II: Problem 16_M

A loaded penguin sled weighing 80 N rests on a plane inclined at angle \( \theta = 20^{\circ} \) to the horizontal (Fig. 6.12). Between the sled and the plane, the coefficient of static friction is \( \mu_s = 0.25 \), and the coefficient of kinetic friction is \( \mu_k = 0.15 \). (a) What is the least magnitude of the force \( \vec{F} \), 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?