A girl is using a rope to pull a box that weighs 300 N across a level surface with constant velocity.The rope makes an angle of 30° above the horizontal,and the tension in the rope is 100 N.What is the normal force of the floor on the box?
A)350 N
B)200 N
C)400 N
D)250 N
E)213 N

Question

Quizplus · Accepted Answer

The normal force is the force exerted by a surface to support the weight of an object resting on it. Since the box is moving with constant velocity, the net force in the vertical direction is zero. The vertical component of the tension in the rope reduces the normal force. The vertical component of the tension is 100 N * sin(30°) = 50 N. Therefore, the normal force is 300 N (weight) - 50 N (vertical component of tension) = 250 N.

A Girl Is Using a Rope to Pull a Box