Question

Let's say you are pushing a 100 N box across the floor with a force of 20 N. If the box is moving at a constant velocity and maintains constant contact with the floor, what must the normal force be?

Answer 1

If the box is moving at a constant velocity and maintains constant contact with the floor, the normal force must be equal in magnitude and opposite in direction to the force you are applying.

In this case, you are applying a force of 20 N in one direction to push the box. According to Newton's third law of motion, the floor exerts an equal and opposite force on the box. Therefore, the normal force exerted by the floor on the box is also 20 N in the upward direction.

So, the normal force on the box must be 20 N.