1. ACTIVITY #5: Bouncing Golf balls! In this activity, we will investigate how a golf ball reacts when dropped onto different surfaces. We will determine how many bounces the ball makes before coming to rest. By interpreting our data, we can reach conclusions about the energy transfers that take place during the collision of the ball and surface Will the dropped golf ball keep bouncing forever? How high will the first bounce be? the second bounce? the third bounce? What effect will changing the surface have on the bouncing of the golf ball? What happens to the ball’s energy when the ball strikes the surface ? GOALS: GOALS: In this lab activity, you will …  Observe how energy is transferred from one object to another object. Explain how these transfers change the motions of the objects involved Explain what happens to each form of energy throughout the activity.  Observe how the physical characteristics of an object and its surface influence its ability to transfer and transform energy.

2. MAIN IDEAS: MAIN IDEAS: The important concepts and skills covered in this activity are …  The energy of a falling ball is transformed from gravitational potential energy to kinetic energy.  When the ball strikes a surface, part of its kinetic energy is transferred to the surface, and as the ball bounces back up, its remaining kinetic energy transforms back into potential energy. Different materials transfer energy at different rates. The kinetic energy transferred to the surface takes the form of organized vibrations of the particles that make up the surface. Through these vibrations, the energy is spread to particles throughout the surface.

3. Activity Overview: Activity Overview: A synopsis of this lesson is as follows… Whenever a ball is dropped onto a horizontal surface, it transfers a fraction of its kinetic energy to the surface. How much of the energy is transferred depends on the physical characteristics of the surface. If a golf ball is used, and dropped onto a very hard surface (a tile or concrete surface for instance) roughly 25% of the ball’s current kinetic energy is transferred to the surface each time it bounces. When dropped on a wooden surface, a larger percentage is transferred. If a golf ball is dropped onto a thick hardbound textbook, the results are very surprising. By releasing a golf ball from rest, one meter above the surface, it is possible to investigate how much energy is transferred to the surface by observing how far up the golf ball bounces. It is also possible to investigate the energy transfer process by counting the number of bounces that the ball makes before coming to rest. More bounces mean that less kinetic energy is transferred to the surface each time contact is made. It is even possible to “feel” the energy transfer by lightly placing your hand on the surface.

4. MAKING SENSE OF ENERGY … How energy is transferred between objects, and how energy is transformed from one form to another affects our daily lives. Children jumping on a trampoline make use of the physical properties (elasticity) of the mesh materials and springs to recover most of their kinetic energy each bounce. Modern cars are designed with crumple zones and other safety features. The crumple zones are designed to absorb much of the car’s kinetic energy in an impact. Auto manufacturers spend millions of dollars every year designing ways to reduce the fraction of the car’s kinetic energy that is transferred to the air and transformed into heat energy by friction within the moving parts of the vehicle. Objects transfer energy to other objects by pushing or pulling on them. Forces, such as gravity, friction between sliding surfaces and forces of collision are responsible for energy transfer from object to object, AND the transformation of energy from one type to another.

5. Part A – Energy Transfers During a “Bounce” Drop the ball onto a hard floor (tile, wood, concrete, etc.) and count the number of bounces needed for the ball to transfer away all of its kinetic energy. Question #1:We will be repeating this experiment for a number of surfaces. What variables do you plan to keep constant, and what variables do you intend to change. Question #2:Why it is important to keep the fixed variables constant? How do you plan to ensure that these fixed variables remain constant throughout the experiment? Keeping in mind which variables you will keep fixed, and which variables you will change, construct a simple data table and then record your data for the choice of variables you just investigated. Repeat the entire experiment using a different impact surface (a rug covered floor, a pad of paper or magazine, a book, etc) and record your data in the data table, make a graph of the results.

6. Question #3:What kind of graph is best suited for displaying the results of your experiments? Question #4:Looking at the data, it is clear that for some surfaces the ball took more bounces before coming to rest than on other surfaces. Which surfaces accepted the most energy per bounce? How do you know this is true ? Question #5:Where do you think the energy transferred to the surface goes? What form does it take? Part B – The Organized Vibrations of Particles - Creating a Shock Wave Place your hand on the (landing) surface and have your lab partner drop the golf ball onto the surface as was done earlier in the activity. Question #6:Did you feel anything in your hand as the ball was striking the surface? If so, describe what you felt and hypothesize what happened to the kinetic energy that was transferred to the surface when it was struck by the ball.

7. Now change surfaces and repeat the process. Question #7:Could you feel any difference from one surface to the next? Is there a relationship between what you felt and how many bounces were needed for the ball to come to rest? Question #8:What characteristics of the surface help determine how much kinetic energy it can absorb? Keep in mind that the energy must go somewhere. Why do some surfaces accept more energy than others during each bounce? Part C – Mechanical Waves Place a clear plastic container partially filled with water (2-3 cm deep) on the surface the golf ball is dropped onto. Wait for the water in the container to come to rest, and drop the golf ball onto the surface nearby BUT NOT INTO the container of water. Question #9:Did you notice any disturbance in the water when the ball struck the surface nearby the container? If so, is the disturbance the same for all surfaces?

8. .Take the container of water and place it on a tabletop. Flick the side with your finger and observe the waveforms at appear. Where does the energy that creates these waveforms come from? Wait a few seconds and describe what happens to the waves in the water. Question #10:What happened to the energy carried by the waves after the water returns to rest? When you drop a ball onto a level surface, it makes a few bounces and then comes to rest. Where did the energy of the ball go? What energy transformations take place? What energy transfers take place? Where has the original potential energy of the golf ball gone when the ball comes to rest?