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?

Question

Physics

Tiffany Jones

7 May, 09:16

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?

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Anabella Barr · Answer 1

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.