Question

An elevator is rising at constant speed. Consider the following statements: 1. the upward cable force is constant 2. the kinetic energy of the elevator is constant 3. the gravitational potential energy of the Earth-elevatorsystem is constant 4. the acceleration of the elevator is zero 5. the mechanical energy of the Earth-elevator system is constant which of them is true and why?

Answer 1

Answer:

Explanation:

Statement 1 is true because the elevator is moving with constant velocity i.e. acceleration and the net force is zero. So upward force is constant

Statement 2 is also true because kinetic energy is proportional to the square of velocity. since v is constant so kinetic energy is constant

Statement 3 is false because gravitational potential energy is a function of height and it is increasing. so Potential energy is increasing.

Statement 4 True, because velocity is constant therefore acceleration is zero.

Statement 5 is false since mechanical energy is the sum of potential and kinetic energy. As potential energy is increasing therefore total energy is increasing w.r.t. to earth.