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Ch 5 Sect 1 The Nature of Energy

Ch 5 Sect 1 The Nature of Energy. Chapter 5 Section 1 – What You’ll Learn Before you read - write the reading’s objectives in this space: 1 – _______________________________________ ____________________________________________________________________________________

melanie-whitney
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Ch 5 Sect 1 The Nature of Energy

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  1. Ch 5 Sect 1The Nature of Energy

  2. Chapter 5 Section 1 – What You’ll Learn Before you read - write the reading’s objectives in this space: 1 – _______________________________________ ____________________________________________________________________________________ 2 – _______________________________________ ____________________________________________________________________________________ 3 - ________________________________________ ____________________________________________________________________________________ 4 - ________________________________________ ____________________________________________________________________________________

  3. Chapter 5 Section 1 – What You’ll Learn Before you read - write the reading’s objectives in this space: 1 – Distinguish between kinetic and potential energy. 2 – Calculate kinetic energy. 3 – Describe different forms of potential energy. 4 – calculate gravitational potential energy.

  4. What is energy? __________________________________________ __________________________________________ __________________________________________ When something has the ability to change its environment Or change its self it has energy. 1

  5. What is energy? The ability to cause change. When something has the ability to change its environment Or change its self it has energy. 1

  6. Change Requires Energy • You use energy to arrange your hair to look the way you want it to. • You also use energy when you walk down the halls of your school between classes or eat your lunch.

  7. Energy has several different forms, what are they? Describe each. __________________________________________ __________________________________________ __________________________________________ __________________________________________ 2

  8. Energy has several different forms, what are they? Describe each: Electrical – flow of electric charge through a conductor Chemical – energy in a substance that can be changed by chemical reaction. Radiant – transmitted by waves Thermal – caused by heat or temperature 2

  9. An Energy Analogy • If you have $100, you could store it in a variety of forms—cash in your wallet, a bank account, travelers’ checks, or gold or silver coins. It can be changed to other forms. • You could deposit your cash into a bank account or trade the cash for gold. • Regardless of its form, money is money. • The same is true for energy. • Energy from the Sun that warms you and energy from the food that you eat are only different forms of the same thing. 3

  10. Define Kinetic energy (KE)? _________________________________________ _________________________________________ What does KE depend on? _________________________________________ What is the formula? What is the SI unit of energy?________ What is the abbreviation? ______ What is a Joule equal to? ___________ 4

  11. Define Kinetic energy (KE)? The energy a moving object What does KE depend on? The objects mass and speed What is the formula? Kinetic energy (J) = ½ X mass (kg) x velocity2 (m2s2) KE = (½ )(m)(v2 ) (2)(KE)= v2 (2)(KE) = m m v2 What is the SI unit of energy? joule What is the abbreviation? J What is a Joule equal to? kg*m2/s2 4

  12. What is the kinetic energy of a beach ball moving at 1.5m/s if the beach ball has a mass of 200g? 5

  13. ( )( )( ) = 1 0.2 kg 1.5 m2 0.225 kg m2 2 s s2 What is the kinetic energy of a beach ball moving at 1.5m/s if the beach ball has a mass of 200g? KE=½ mv2 0.23 J 5

  14. A toy car is moving at a speed of 2m/s and has a KE of 0.24J. What is the car’s mass? 6

  15. A toy car is moving at a speed of 2m/s and has a KE of 0.24J. What is the car’s mass? (2)(KE) = m v2 (2) (0.24 J kg m2/s2) = 0.12kg (2m/s)(2m/s) 6

  16. Even motionless objects can have energy. This energy is stored in the object. • A hanging apple in a tree has stored energy. • What is stored energy due to position called? _____________________________________________ 7

  17. Even motionless objects can have energy. This energy is stored in the object. • A hanging apple in a tree has stored energy. • What is stored energy due to position called? Potential Energy (PE) 7

  18. If the apple stays in the tree, it will keep the stored energy due to its height above the ground. Potential Energy (PE) • If it falls, that stored energy of position is converted to energy of motion. Kinetic Energy (KE) 8

  19. If you stretch a rubber band and let it go, it sails across the room. • As it flies through the air, it has kinetic energy due to its motion. • Where did this kinetic energy come from? • ________________________________________ • What is EPE?________________ • _____________________________ • _____________________________ • ______________________________ • ______________________________ 9

  20. If you stretch a rubber band and let it go, it sails across the room. • As it flies through the air, it has kinetic energy due to its motion. • Where did this kinetic energy come from? • Elastic Potential Energy • What is EPE? Energy stored by • something that can stretch or • compress, such as a rubber band • or spring. 9

  21. What is Chemical Potential Energy? _________________________________________ _________________________________________ _________________________________________ 10

  22. What is Chemical Potential Energy? Energy stored in chemical bonds 10

  23. Energy is stored in the bonds that hold the carbon and hydrogen atoms together and is released when the gas is burned. • In this chemical reaction, chemical potential energy is released.

  24. Define Gravitational Potential Energy: _________________________________________ _________________________________________ _________________________________________ _________________________________________ What is the formula for GPE? • On Earth the acceleration of gravity is 9.8 m/s2, and has the symbol G. 11 • Like all forms of energy, gravitational potential energy is measured in joules.

  25. Define Gravitational Potential Energy: • Anything that can fall has stored energy called gravitational potential energy. • (GPE) is energy stored by objects due to their position above Earth’s surface. What is the formula for GPE? GPE = h GPE = G GPE = m mG mh Gh 11

  26. Changing GPE • According to the equation for gravitational potential energy, the GPE of an object can be increased by increasing its height above the ground. • Use MGH to find GPE of a ball at two different heights. • First ball: Second ball: • M= 0.30kg M=0.30kg • G= 9.8m/s2 G=9.8m/s2 • H=5m H=10m 12

  27. Changing GPE • According to the equation for gravitational potential energy, the GPE of an object can be increased by increasing its height above the ground. • Use MGH to find GPE of a ball at two different heights. • First ball: Second ball: • M= 0.30kg M=0.30kg • G= 9.8m/s2 G=9.8m/s2 • H=5m H=10m .3kg(9.8m/s2)(5m) = 14.7J .3kg(9.8m/s2)(10m) = 29.4J 12

  28. Changing GPE • If two objects are at the same height, then the object with the larger mass has more gravitational potential energy. • Use MGH to find GPE of a ball at two different masses. • First ball: Second ball: • M= 0.30kg M=0.20kg • G= 9.8m/s2 G=9.8m/s2 • H=5m H=5m 13

  29. Changing GPE • If two objects are at the same height, then the object with the larger mass has more gravitational potential energy. • Use MGH to find GPE of a ball at two different masses. • First ball: Second ball: • M= 0.30kg M=0.20kg • G= 9.8m/s2 G=9.8m/s2 • H=5m H=5m .2kg(9.8m/s2)(5m) = 9.8J .3kg(9.8m/s2)(5m) = 14.7J 13

  30. What is the height of an object dropped if it has a mass of 1.2kg and a GPE of 176.4J? 14

  31. What is the height of an object dropped if it has a mass of 1.2kg and a GPE of 176.4J? GPE = h mG 176.4 J Kg m2 /s2 = 15m (1.2 kg) (9.8m/s2) 14

  32. An astronaut drops a tool from a height of 4m on the moon. The moon’s gravity is 1.67 m/s2 and the GPE is 16.7J. What is the tool’s mass? What is that in pounds ? 15

  33. An astronaut drops a tool from a height of 4m on the moon. The moon’s gravity is 1.67 m/s2 and the GPE is 16.7J. What is the tool’s mass? What is that in pounds ? GPE = m Gh 16.7 J kg m2 /s2 = 2.5kg (1.67 m/s2) (4 m) ( )( )= 2.5 kg2.205 lb 5.51 lb 1 1 kg 15

  34. Section Check 1 Question 1 Energy is the ability to cause __________. A. change B. heat C. motion D. work 16

  35. Section Check 1 Answer The answer is A. Energy is the ability to cause change and has several different forms. 16

  36. Section Check 1 Question 2 What are the four different forms of energy? 17

  37. Section Check 1 Question 2 What are the four different forms of energy? Answer The four different forms of energy are electrical, chemical, radiant and thermal. 17

  38. Section Check 1 Question 3 The kinetic energy of an object depends on __________. A. the object’s mass and speed B. the object’s mass C. the object’s speed D. the acceleration of the object 18

  39. Section Check 1 Answer The answer is A. Kinetic energy depends on both the mass and speed of the moving object. 18

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