An elevator is being lifted at a constant speed by a cable attached to a

motor. There is no air resistance, nor is there any friction between the

elevator and the walls of the elevator shaft. The weight of the elevator

is equal in magnitude to the upward force that the cable exerts on the

elevator. Is this a consequence of Newton$$s first law or Newton$$s third

law? Does the cable do positive, negative or zero work on the elevator?

Is the total work done on the elevator positive, negative or zero? Explain

your answers.