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?

Friction

Explanation:

Assuming that the box is moving forwards, - 7N would have to be friction, and 14N is the push force applied to the box.

-7N cannot be equal to gravity because the normal force and force of gravity must cancel out, so gravity would be - 10N and normal force is 10N.