Question

A box is standing on a conveyor belt that is not in motion. At one point the belt starts moving with some acceleration. At that point the box starts moving too (without slipping). Which force is responsible for the acceleration of the box. a. The air resistance force. b. The force of the pull. c. The force of friction. d. The normal force.

Answer 1

Given that a box is standing on a conveyor belt that is not in motion.

When the belt starts moving with some acceleration, the box starts moving too without slipping.

Let's determine the force that is responsible for the acceleration of the box.

Here, since the box starts moving without slipping when the belt starts moving, there will be static friction between the box and the belt since the belt was fixed.

Now, the force which is responsible for the acceleration of the box will be the force of gravity and the normal force.

Applying the Newton's second law, if the there is only force of gravity and the normal force acting on the box, there will be zero horizontal acceleration.

In order for the box to accelerate without slipping, the force responsible will be the static frictional force.

ANSWER:

c. The force of friction.