CP Science 9
That's the Way the Ball Bounces Lab
INTRODUCTION:
Can you explain the bounce of a ball? When you hold a ball above the floor, its mass and height give it gravitational potential energy. When you drop it, an energy transformation takes place. What happens to the potential energy? Since the ball begins to move, some of the potential energy must become kinetic energy (the energy of moving objects). When the ball bounces back up and hangs motionless for an instant before failing again, it no longer has any kinetic energy. Has it all been transformed back into potential energy? If not, where did the energy go? Each material has quality called coefficient of restitution that describes its ability to bounce. The coefficient of restitution is calculated by dividing potential energy of the ball at the height of its bounce (PEf) by its potential energy at its starting height (PEi).
PURPOSE:
Investigate the energy conversion of a bouncing ball and determine its coefficient of restitution.
MATERIALS:
Superball
tennis ball
a meter stick
PROCEDURE:
1.Copy the DATA table on a sheet of paper.
2.Hold the meter stick vertically on a hard, flat surface. (A tile or concrete floor works best; using a table top is acceptable.) Place the stick so that the 1-cm mark is nearest the floor and the 99-cm mark is nearest the ceiling.
3.Hold one of the balls 1 M (100 cm) above the surface, and about 15 cm in front of the meter stick. This is the starting height.
4.Release the ball. Avoid spinning the ball as you release it, or it will not bounce straight up. Determine (in centimeters) how high the ball bounces. This is the bounce height.
5.Record the bounce height in the data table:
6.Repeat steps2, 3, and 4 three more times. Enter the bounce height for each of the four trials in the data table.
7.Determine the bounce height of the other ball. Repeat the procedure given in steps 2, 3, and 4. Record the results of your four trials of the second ball in the data table.
8.Answer the DATA ANALYSIS questions in complete sentences.
DATA:
Trial / Starting Height / Superball Bounce Height / Tennis Ball Bounce Height1 / 100 cm
2 / 100 cm
3 / 100 cm
4 / 100 cm
DATA ANALYSIS: (Answer in complete sentences)
1.What is the average bounce height for a Superball dropped from a height of 100 cm?
2.What is the average bounce height for a tennis ball dropped from a height of 100 cm?
3.Is the average bounce height for each of the balls greater than, less than, or equal to the original starting height of 100 cm?
4.The higher the ball, the more gravitational potential energy the ball has stored in it. When the ball reaches its average bounce height, does it have
the same amount of gravitational potential energy or
less gravitational potential energy or
more gravitational potential energy
than it had while it was being held 1 m above the surface?
5.Since kinetic energy is determined by the mass and the velocity of an object, the faster the ball is moving, the greater its kinetic energy will be (as either mass or velocity increases, so does the kinetic energy). When will the ball have the greatest amount of kinetic energy,
before it is released or
immediately after it is released or
just before it strikes the surface?
6.Complete the following statements: When the ball's gravitational potential energy is large, its kinetic energy will be _____ (large/small). When the ball is moving fast and it contains a large amount of kinetic energy, the amount of gravitational potential energy it contains will be _____ (large/small).
7.The kinetic energy of a moving ball is changed (converted) into other forms of energy when it hits a surface and bounces. Which of the following energy forms do you think is (are) produced as the ball strikes the floor?
SoundChemical potential energy
LightKinetic energy
Electrical energyNuclear energy
HeatElastic potential energy
Explain your choice(s).
8.Calculate the coefficient of restitution of each ball. Show your work for full credit.
9.How much mechanical energy is converted into heat energy for each ball (Suppose the mass of superball and tennis ball are 50 g and 150 g, respectively)?