A 55-kg box rests on a horizontal surface.The coefficient of static friction between the box and the surface is 0.30.A horizontal 140-N force is applied to the box.What is the friction force on the box?
A)140 N
B)160 N
C)16.5 N
D)0.00 N
E)42 N

Question

Quizplus · Accepted Answer

The friction force equals the applied force (140 N) because it's less than the maximum static friction force, which can be calculated as the product of the coefficient of static friction (0.30) and the normal force (mass * gravity, 55 kg * 9.8 m/s^2 = 539 N). The maximum static friction force is 0.30 * 539 N = 161.7 N, and since 140 N is less than this, the friction force matches the applied force to prevent motion.

A 55-Kg Box Rests on a Horizontal Surface