Question

An elevator is moving upwards at a constant speed. Ignoring any friction, which statement is correct ?

• A. The kinetic energy of the elevator is constant.
• B. The gravitational potential energy of the Earth-Elevator system is constant.
• C. The mechanical energy of the Earth-Elevator system is constant.
• D. (A) and (C) are both correct, but (B) is not correct

Answer 1

The correct option is A The kinetic energy of the elevator is constant.

As the elevator is moving at a constant speed, its kinetic energy is also constant. The gravitational potential energy of the Earth-Elevator system is increasing as the separation between the two objects is increasing. The total mechanical energy of the system is the sum of the kinetic and gravitational potential energies in this case, so it is also increasing.