Topic: Energy Transformations

Pre-Assessment ____ 1. Emily is riding her bicycle. Which BEST explains why only some of the energy used to pedal her bicycle is transferred into forward motion of the bicycle?

A The energy of the bicycle tire is applied in a circular motion. B The energy of the bicycle is transferred to only one wheel. C The gears and chain of the bicycle are covered with oil. D The gears and chain of the bicycle generate friction.

____ 2. A wind generator transfers wind energy into electrical current.

How does the amount of energy in the electrical current compare to the amount of wind energy that turns the blades on the wind generator?

A There is less energy because some heat is produced in the transfer. B There is less energy because wind does not blow with a constant force. C There is more energy because electrical energy can be stored in batteries. D There is more energy because there is more than one blade on the generator.

3 Student Exploration: Roller Coaster Physics

Name: ______Date: ______

Reporting Category: Physical Science Benchmark SC.7.P.11.2 Investigate and describe the transformation of energy from one form to another. (Also Assesses SC.6.P.11.1 and SC.7.P.11.3)

Prior Knowledge Questions (Do these BEFORE using the Gizmo.) An object’s momentum reflects how easy it is to stop. Objects with greater momentum are harder to stop and can also inflict more damage when they collide with other objects.

1. Which do you think has more kinetic energy, a moving car or a moving train? ______

2. The speed of an object is how fast it is moving. Which has more kinetic energy, a car with a speed of 15 km/h (kilometers per hour) and a mass of 250kg or a car moving at 150 km/h and a mass of 20kg? ______

3. What are the two factors that affect an object’s kinetic energy?______

4. Can you explain how the transformation of potential energy into kinetic energy and vice versa proves the Law of Conservation of Energy? ______

Gizmo Warm-up The Roller Coaster Physics Gizmo™ shows a toy car on a track that leads to an egg. You can change the track or the car. For the first experiment, use the default settings (Hill 1 = 70 cm, Hill 2 = 0 cm, Hill 3 = 0 cm, 35-g car).

1. Press Play ( ) to roll the 35-gram toy car down the track. Does the car break the egg? ______

2. Click Reset ( ). Raise Hill 1 to 100 cm, and click Play again. Does the car break the egg? ______

3. Click Reset. Lower Hill 1 back to 70 cm and select the 50-gram toy car. Click Play. Does the 50-gram car break the egg? ______

4. What factors determine whether the car will break the egg? ______

4 Activity A: Get the Gizmo ready: The speed of a  Click Reset. roller coaster  Select the 35-g toy car.

Question: What factors determine the speed of a roller coaster?

1. Observe: Set Hill 1 to 100 cm, Hill 2 to 0 cm, and Hill 3 to 0 cm. Be sure the Coefficient of friction is set to 0.00. (This means that there is no friction, or resistance to motion.)

A. Click Play. What is the final speed of the toy car? ______

B. Try the other cars. Does the mass of the car affect its final speed? ______

2. Collect data: Find the final speed of a toy car in each situation. Leave the last column blank.

Hill 1 Hill 2 Hill 3 Final speed 40 cm 0 cm 0 cm 40 cm 30 cm 0 cm 60 cm 50 cm 20 cm 60 cm 0 cm 0 cm 60 cm 45 cm 0 cm 90 cm 75 cm 30 cm

3. Analyze: Look at the data carefully. Notice that it is organized into two sets of three trials.

A. What did each set of trials have in common? ______

B. Did hill 2 have any effect on the final speed? ______

C. Label the last column of the table Total height lost. Fill in this column by subtracting the height of hill 3 from the height of hill 1.

D. What do you notice about the Total height lost in each set of trials? ______

______

4. Draw conclusions: When there is no friction, what is the only factor that affects the final speed of a

roller coaster? ______

What factors do not affect the final speed of a roller coaster? ______

______

5 Get the Gizmo ready: Activity B:  Click Reset. Energy on a roller  Set Hill 1 to 100 cm, and Hill 2 and 3 to 0 cm. coaster  Select the 50-g car.

Question: How is energy expressed in a moving roller coaster?

5. Observe: Turn on Show graph and select E vs t to see a graph of energy (E) versus time. Click Play and observe the graph as the car goes down the track.

Does the total energy of the car change as it goes down the hill? ______

6. Experiment: The gravitational potential energy (U) of a car describes its energy of position. Click Reset. Set Hill 3 to 99 cm. Select the U vs t graph, and click Play.

a.A. What happens to potential energy as the car goes down the hill? ______

a.B. What happens to potential energy as the car goes up the hill? ______

7. Experiment: The kinetic energy (K) of a car describes its energy of motion. Click Reset. Select the K vs t (kinetic energy vs. time) graph, and click Play.

A. What happens to kinetic energy as the car goes down the hill? ______

B. What happens to kinetic energy as the car goes up the hill? ______

8. Compare: Click Reset. Set Hill 1 to 80 cm, Hill 2 to 60 cm, and Hill 3 to 79 cm. Be sure the 50-g toy car is selected, and press Play. Sketch the U vs t, K vs t, and E vs t graphs below.

9. Draw conclusions: Based on the graphs, how are potential energy, kinetic energy, and total energy related to one another? ______

10. Describe the transfers of energy that occur as the car races along the track?

6 ______

Extension

Explain the Energy Transformation:

Station 1 – Battery operated flashlight: ______

Station 2 – Pendulum

______

Station 3 – Windmill:

______

Station 4 – Battery operated light switch:

______

Station 5 – Balloon Rocket (A balloon powered straw attached to a string anchored at an incline):

______

7 Assessment

____1 A student builds a simple electric circuit.

What are the main types of energy produced in this circuit when the switch is closed? A thermal and light B sound and thermal C light and magnetism D magnetism and sound

____ 2 Dams are built on rivers to hold back water.

The water is then released and passes through turbines to produce F solar energy. G thermal energy. H chemical energy. J electrical energy.

____ 3 Valerie and Greg want to bake a cake. They mix the cake batter and preheat the oven. Once the oven reaches the right temperature, they pour the batter in a cake pan, put it in the oven, and close the door. They know that while the cake is in the oven, a chemical change that involves energy occurs.

Which of these statements describes the amount of energy in the oven while the cake is baking?

8 A The total amount of energy increases because the oven gets very hot. B The total amount of energy decreases because it changes into matter. C The total amount of energy stays the same, but it changes from one form to another. D The total amount of energy will either increase or decrease, depending on how much cake batter there is.

____ 4 Jenna's dog eats a mixture of dry and canned dog food. When she feeds him, she pours some dry dog food into a bowl and gets a can of dog food out of the pantry. She plugs an electric can opener into an outlet to open the can. To open the can, the can opener converts electric energy into which of the following?

F chemical energy G mechanical energy H potential energy J radiant energy

____5 The line shows the path of the ball.

As the ball moves from Point 3 to Point 4, which energy conversion is taking place?

A thermal to static B static to thermal C potential to kinetic D kinetic to potential

____ 6 Brittany pedaled her bicycle quickly on a level surface. When she quit pedaling and coasted, the bicycle slowed and came to a stop. What happened to the energy of the moving bicycle as it coasted to a stop?

F It was given off due to friction. G It was reabsorbed into Brittany’s joints and muscles. H It was stored in the bicycle wheels as potential energy. J It was transferred to the air in the form of visible light.

____ 7 Alicia gives her brother a push while he is seated on a swing. She finds that after a few seconds, she needs to push again to keep him going. The reason her brother slows down is because the mechanical energy is converted into

A potential energy that heats the air. B chemical energy that moves the swing. 9 C kinetic energy that makes the swing slow down. D thermal energy that is released into the atmosphere.