Chapter 11, Problem 81A

To determine

To Explain: The kinetic energies and speeds of the balls as they strike the ground.

Answer to Problem 81A

The kinetic energies and speeds of both the balls are same as they strike the ground.

Explanation of Solution

Introduction:

Kinetic energy: Kinetic energy of a body is the energy it gained by virtue of its motion. It depends on both mass and velocity of motion of a body.

Potential energy: Potential energy of a body is the energy it holds due to its position. It depends both on its mass and its position with respect to other bodies.

It is given that two balls are identical, hence the mass of the two balls are equal. Also, two balls are thrown from the top of a cliff, each with the same initial speed. Hence the kinetic energy and potential energy of both the balls are equal even if they are moving in reverse directions. Therefore, during the time of striking the ground, they possess equal speeds and kinetic energies.