Question

A person is pushing a box across a table. The measured forces on the box are 10N, 14N, 7N, 10N. Which force is represented by 7N? force of friction normal force force of gravity push force

Answer 1

The answer is C. Force of gravity

Answer 2

Answer: The friction force.

Justification:

Since the box is sliding over the table, the normal force equals the weight of the object (and any other vertical force that is applied on the box).

So, the normal force and weight (along with any other vertical component of a force applied on the box) must be 10 N and 10 N.

The other two forces: 14 N and 7 N are the forces in the plane of the table and should be opposite in a same line. The 14 N force is the responsible of the motion and the 7N force is opposing the 14 N force, so the 7N force has to be the friction force. Of course, 14N - 7N > 0 which is why the box is moving.