A trunk with a weight of 160 N rests on the floor. The coefficient of static fri

Question

A trunk with a weight of 160 N rests on the floor. The coefficient of static friction between the trunk and the floor is 0.47, and the coefficient of kinetic friction is 0.28. (a) What is the magnitude of the minimum horizontal force with which a person must push on the trunk to start it moving? (b) Once the trunk is moving, what magnitude of horizontal force must the person apply to keep it moving with constant velocity? (c) If the person continued to push with the force used to start the motion, what would be the magnitude of the trunk's acceleration?

Explanation / Answer

a) to start movement , force equals to static friction is required.

static friction = u_s mg = 0.47 x 160 = 75.2 N

b) once started after that to keep moving , force equals to kinetic friction is required.

kinetic friction = u_k mg = 0.28x 160 = 44.8 N

c) Fnet = (force applied = static friction) - kinetic friction = ma

75.2 -44.8 = (160/9.81)a

a = 1.86 m/s2

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