Question

short answer questions：

7. Ball Bounce

Explain the relationship between the work done on a ball and the resulting transformation of energy. Identify each type of energy as the ball is released from a height up to an including the rebound of the ball and its achieved height from bouncing.

Answer 1

When a ball hits the floor, most of its kinetic energy (KE = 1/2 mv^2) is converted in a form of potential energy (mgh) call elastic potential energy​. This is energy that is stored in the ball as its shape is changed by hitting the floor. The part of the kinetic that is not​ converted into elastic potential energy is changed into sound energy (the thump you hear), a small increase in the heat of the ball and the ground, and heating the air molecules as the ball falls through it.

When the ball bounces back up from the ground its elastic potential energy is converted back into kinetic energy and gravitational potential energy as the ball resumes its original shape. A ball that is dropped (not thrown) never​bounces back up to the original height, and will rise less with each bounce. This is because each time it strikes the floor some of its kinetic energy is converted into non­ useable heat and sound energy. Some balls, however, are more efficient in how they store and release their elastic potential energy than others. You can estimate that efficiency by measuring the height of the ball’s rebound and calculating what percentage it is of the original height from which the ball was dropped. The more efficiently a ball stores and converts elastic potential energy back into kinetic energy, the higher the ball bounces