A 150-N box is being pulled horizontally in a wagon accelerating uniformly at 3.00 m/s².The box does not move relative to the wagon,the coefficient of static friction between the box and the wagon's surface is 0.600,and the coefficient of kinetic friction is 0.400.The friction force on this box is closest to A)450 N. B)90.0 N. C)60.0 N. D)45.9 N.

Question

Quizplus · Accepted Answer

The force pulling the box in the wagon is the force of the wagon on the box (equal in magnitude and opposite in direction to the force of the box on the wagon). This force is found using Newton's second law: 
F = ma = (150 N)(3.00 m/s^2) = 450 N 
The force of friction between the box and the wagon's surface must be equal in magnitude and opposite in direction to this force. Since the box is not moving relative to the wagon, the static friction force must be used: 
Ff = μsFn = (0.600)(150 N) = 90 N 
This is the friction force acting on the box.

A 150-N Box Is Being Pulled Horizontally in a Wagon