This lab is fairly trivial and is designed to get you to make some measurements and to show how potential energy is converted to kinetic energy at a rate that is dictated by energy conservation. The variables involved are height (H), mass (m) of ball, velocity at impact, and the elasticity of the surface. The relevant relations are:

Potential Energy (PE) = mgh
Kinetic Energy (KE) = 1/2mv²

(g gravitational acceleration of earth = 9.8 meters/sec²)

Energy conservation asserts that in a closed system energy is conserved. In the case of the falling ball, this means that the sum of PE+KE is a constant. When the object is at rest at some height, h, then all of its energy is PE. As the object falls and accelerates due to the earth's gravity, PE is converted into KE. When the object strikes the ground, h=0 so that PE=0, the all of the energy has to be in the form of KE and the object is moving it at its maximum velocity. (In this virtual lab we are ignoring air resistance).

This appartus will drop a mass from different heights. When the mass strikes the ground, some percentage of its original energy will be absorbed by the ground. The parameters you control are:

• The Total Energy (Energy)
• The mass of the object (Mass)
• The percentage of the energy which is absorbed by the surface on each "bounce" (EAS)

In addition you can measure the height of the object by clicking on it. The impact velocity of the object will also be given at each bounce. The functionality of the buttons are as follows:

• Start = Drop the ball after Energy, Mass and EAS have been set; resume after step or pause has been selected
• Step = Drop the ball once and it rebounds to its maximum height and then pauses
• Reset = Reset experiment to intial values
• Pause = Pause the animation at any point

select m =4 kg; Energy =400 J; EAS = 50%

1. What is the height of the ball? (verify by measuring it and using the formula)
2. How high will the ball bounce on the first bounce (verify by selecting step and measuring the height)
3. Determine the impact velocity of the ball on the first bounce by combing the formula for PE and KE; verify your calculation with the actual experiment.
4. Hit reset and change the mass of the ball to 16 KG. Do you expect the impact velocity to be more or less than in the case of the 4 KG ball? Explain your reasoning and then test it.
5. Now determine and enter in the values that will produce the lowest height of the ball
6. Now determine and enter in the values that will produce the highest height of the ball.
7. Hit reset and now set EAS to 25%. Which combination of parameters do you think will allow the ball to bounce the most number of times? Enter in those values in the worksheet
8. Finally, determine which combination of parameters, EAS, Energy and mass will produce a situation where the velocity of the ball on the third bounce will be 5.0 m/s.

When done, submit your worksheet by clicking on the words "publish to global view" (the first item under reporting tasks).