Chapter 4 – Energy

1. Chapter 4 – Energy 4.1 What is Energy?

2. I. Essential Question • How are Energy, Work, and Power Related? • What are the two main types of energy?

3. II. Key Vocabulary • Energy: the ability to do work or cause change • Kinetic energy: the energy of an object in motion • Potential energy: the energy an object has due to its position or shape

4. II. Key Vocabulary • Gravitational potential energy: PE related to an object’s height • Elastic potential energy: PE associated with an object that can be compressed or stretched.

5. III. Key Concepts • Since energy is similar to work, it can be substituted in the following formula: • Power = Work / time • Power = Energy / time

6. III. Key Concepts • The two basic types of energy are kinetic and potential. • Kinetic energy (of motion) depends on an object’s speed and mass. • The faster the object moves, the greater the KE. • The more mass an object has, the greater the KE.

7. III. Key Concepts • Kinetic Energy can be found by the following formula: • KE = (1/2)(m)(s2) • KE = (0.5)(m)(s2) • Notice that speed is squared. This means that if the mass is doubled, KE is doubled. If the speed is doubled, the KE is quadrupled.

8. III. Key Concepts • The gravitational PE of an object is equal to the work done to lift the object to that height. • GPE = (weight)(height) • When an object is stretched (like a spring or a rubber band), it has greater elastic potential energy.

9. IV. Exploration • Question: How does mass affect how many times a ball will bounce before stopping? • Hypothesis: When the mass of the ball (increases, decreases) ____________________ then the number of bounces will (increase, decrease) _________________ because ____________________. • Materials: • Meter stick • golf ball • Tennis ball • Ping pong ball • Marble

10. IV. Exploration • Procedures: • Have one member of the group hold the meter stick upright with the zero mark on the table. • Have a second member of the group drop the tennis ball from the top of the meter stick (100cm mark) in such a way that it does not touch the meter stick on the way down. • Have a third member of the group count the number of bounces. The number of bounces should be called out to the fourth member of the group, who should record it in the data table. Repeat for 4 additional trials. • Repeat steps 1, 2, and 3 with each of the other balls until all balls have been tested. • On the graphs, label the axis, and plot the average number of bounces for each ball.

11. IV. Exploration Data Analysis 

12. V. Understanding and Applying • Make the graph AND answer the following questions on a separate sheet of paper. • Answer the questions using the following key terms. (gravitational potential energy; kinetic energy; energy conversion, mechanical energy, mass) • Which ball retained the greatest percentage of its kinetic energy on each bounce? Why? • What can't a ball bounce higher that the height from which it is dropped? • The law of conservation states that: • Explain how the law of conservation applies to this experiment?

13. Chapter 4 - Energy 4.2 Forms of Energy

14. Essential Question How can you find an object’s mechanical energy? What are other forms of energy?

15. Key Vocabulary Mechanical energy: the form of energy associated with the motion position or shape of an object Nuclear energy: type of potential energy; stored in the nucleus of an atom and released during a nuclear reaction. Thermal energy: the total kinetic and potential energy of the particles in an object.

16. Key Vocabulary Electrical energy: the energy of electric charges. Electromagnetic energy: a form of energy that ravels through space in waves. Chemical energy: potential energy stored in chemical bonds.

17. Key Concepts • ME (mechanical energy) is a combination of KE and PE. • It can be calculated by adding the two together; • ME = KE + PE • Objects with ME can do work. • The more ME an object has, the more work it can do.

18. Key Concepts • All objects are made of atoms and all atoms have a nucleus. • Nuclear fission occurs when a nucleus is split. • Nuclear plants use this to create electricity • Nuclear fusion occurs when multiple nuclei join together.

19. Key Concepts

20. Key Concepts The higher the temperature of an object, the greater its thermal energy. The faster the particles move, the more KE they have, and the greater their thermal temp.

21. Key Concepts If electricity is moving, like lightning, then it is KE; if it is still, like static electricity, then it is PE.

22. Key Concepts Chemical bonds exist in food particles; they hold atoms together. When chem bonds are broken, energy is released.

23. Chapter 4 - Energy 4.3 Energy Transformations and Conservation

24. Essential Question How are different forms of energy related? What is the law of conservation of energy?

25. Key Vocabulary Energy transformation: a change from one form of energy to another. Law of conservation of energy: when one form of energy is transformed into another, no energy is lost in the process; energy cannot be created or destroyed.

26. Key Concepts • All forms of energy can be transformed into other forms of energy. • Single transformation examples: • Electrical energy turned into thermal energy to toast bread • Chemical energy transformed into ATP (usable energy) in muscles

27. Key Concepts • Multiple transformation example: • Lighting a match takes several transformations; it involves ME, thermal energy, chemical energy, and electromagnetic energy that we can see.

28. Key Concepts • KE and PE transformations: • Bouncing a ball – when the ball hits the ground and reaches the top of its bounce it has PE; when it is falling down and bouncing up it is gaining KE. • Pendulum – at the top of its swing on either side is when the object has its greatest PE; at the middle of its swing is when it has its greatest KE.

29. Key Concepts

30. Key Concepts • The total amount of energy is the same before and after any transformation. • Whenever friction/air resistance is present, some KE is changed into thermal energy. • Remember…machines cannot be 100% efficient because of friction; work and energy are equivalent.