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 exerted on the box.What is the friction force exerted by the surface 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 exerted by the surface on the box equals the applied force (140 N) because it is 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 (the weight of the box, which is mass times gravity, 55 kg * 9.8 m/s^2 = 539 N). The maximum static friction force is 0.30 * 539 N = 161.7 N, which is greater than the applied force, meaning the box does not move, and the frictional force matches the applied force to prevent motion.

A 55-Kg Box Rests on a Horizontal Surface