3. O BJECTIVES D AY 2 1. I will know (knowledge): that kinetic energy is energy of motion. 2. I will know (knowledge): that potential energy is energy of position. 3. I will be able to (skill): apply the concept of kinetic energy and potential energy to a given situation.

4. In an avalanche, a mass of loose snow, soil, or rock suddenly gives way and slides down the side of a mountain. Describe the amount of energy released. The avalanche releases a great amount of energy.

5. How are energy and work related? Energy is the ability to do work. Work is the transfer of energy. Both work and energy are typically measured in joules (J).

6. Energy has different forms. The sun gives off energy in the form of heat and light. Plants convert sunlight into food. People convert food energy into muscle movement.

7. The energy of motion is called kinetic energy. Turn to a partner: Kinetic energy depends on what factors? Answer: The kinetic energy of any moving object depends upon its mass and speed.

8. S MALL GROUP : WHAT ARE SOME EXAMPLES OF KINETIC ENERGY ?

9. IF THEY HAVE THE SAME VELOCITY, WHICH WOULD HAVE MORE KE? D ISCUSS WHY. CAR TRUCK Small group:

10. ANSWER: THE TRUCK! WHY? Small group:

11. MORE MASS! CAR TRUCK Small group:

12. K INETIC E NERGY EQUATION KE = ½ mv 2 m = mass (kg) v = velocity (m/s)

13. 1. What would happen to the kinetic energy if you would double the mass? 2. What would happen to the kinetic energy if you would double the speed? KE = ½ mv 2

14. 1. KE = ½ mv 2 KE m double the mass then you would double your Kinetic Energy They are a linear relationship!

15. 1. KE = ½ mv 2 KE m double the velocity then you would quadruple your kinetic energy

16. Modeled Practice – Think Aloud A 0.10 kilogram bird is flying at a constant speed of 8.0 m/s. What is the bird’s kinetic energy?

17. Read and Understand What information are you given? What unknown are you trying to calculate? The Kinetic Energy (KE) of the bird.

18. Plan and Solve What equation contains the given quantities and the unknown? Substitute the known values in the formula for KE.

19. JOULE! Science gives kg ∙ m 2 /s 2 A SPECIAL NAME

20. Turn to a partner: Is your answer reasonable? It seems reasonable, because the bird has a low mass, so it would not have much kinetic energy.

21. 1. A 70 kilogram football player is jogging at a speed of 2.0 m/s. What is his kinetic energy?

22. A 70 kilogram football player is jogging at a speed of 2.0 m/s. What is his kinetic energy? Givens: 70 kg = m 2.0 m/s = v Unknown: KE Equation: KE = ½ mv 2 Plug in numbers: KE = ½ (70 kg)(2.0 m/s) 2 KE = ½ (70 kg)(4 m 2 /s 2 ) KE = 560 kg ∙ m 2 /s 2 What is a kg ∙ m 2 /s 2 ? KE = 560 J Joule

23. A 1400 kg car is moving at a speed of 25 m/s. Find the kinetic energy of the car. Givens: 1400 kg =m 25 m/s = v Unknown: KE Equation: KE = ½ mv 2 Plug in numbers: = ½ (1400 kg)(25 m/s) 2 = ½ (1400 kg) (625 m 2 /s 2 ) KE = 437,500 J

24. An object’s gravitational potential energy depends on its mass, its height, and the acceleration due to gravity. Gravitational Potential Energy

25. How would you define gravitational potential energy? Potential energy is energy that is stored as a result of position or shape.

26. Explain the physics behind what happens when a musician pulls the string of his cello to one side, the string is stretched and the bow flies away.

27. The musician adds energy to the cello string by plucking it. When the string is stretched it gains potential energy. Then it is transferred to the bow and turns into kinetic energy.

28. When an object’s height is raised to a higher level, the gravitational potential energy increases.

29. This diver has gravitational potential energy as she stands at the end of a diving board. She gained the potential energy by doing work— by climbing up the steps to the diving board.

30. The unit for mass ‘m’ is kilogram. The unit for height ‘h’ is meter. Acceleration due to gravity, g, has a value in SI units of 9.8 m/s 2 on Earth. The unit for gravitational potential energy is joules.

31. Height is measured from the ground or floor or some other reference level.

32. Small Group: 1. If you double the mass of an object, what happens to the PE? 2. If you double the height you drop an object, what happens to the PE?

33. 1. PE = mgh PE m double the mass then you would double your Potential Energy They are a linear relationship!

34. 2. PE = mgh PE h double the height then you would double your Potential Energy They are a linear relationship!

35. What is the potential energy relative to the water surface of a diver at the top of a 10.0 meter high diving platform? Suppose the diver has a mass of 50.0 kilograms. PE = mgh

36. Givens: 10.0 m = h 50.0 kg = m What does g equal? g = 9.8 m/s 2 Unknown: PE Equation: PE = mgh Plug in numbers: = (50.0 kg )(9.8 m/s 2 )(10.0 m) = 4,900 J

37. I NDEPENDENT P RACTICE 1. What is the unit for kinetic energy? 2. What is the kinetic energy of a 30 kg tiger chasing a deer at a rate of 4 m/s? 3. What is the unit for potential energy? 4. What is the potential energy of a 0.20 kg apple falling from a tree branch at a height of 5 meters?

38. I NDEPENDENT P RACTICE 1. What is the unit for kinetic energy? Answer: Joule 2. What is the kinetic energy of a 30 kg tiger chasing a deer at a rate of 4 m/s? Givens: 30 kg = m 4 m/s = v Unknown: KE Equation: KE = ½ mv 2 Plug in numbers: = ½ mv 2 = ½ (30 kg)(4 m/s) 2 KE = 240 joules

39. I NDEPENDENT P RACTICE 3. What are the units of potential energy? Answer : Joule 4. What is the potential energy of a 0.20 kg apple falling from a tree branch at a height of 5 meters? Givens: 0.20 kg = m 5 m = h g = 9.8 m/s 2 Unknown: PE Equation: PE = mgh Plug in numbers: (0.20 kg)(9.8 m/s 2 )(5 m) PE = 9.8 J

40. 1.What is kinetic energy? 2.What is potential energy? 3.What is the unit for KE & PE?

41. 1.What is kinetic energy? the energy due to an object’s motion 2. What is potential energy? the energy due to an object’s position 3.What is the unit for PE & KE? joule

42. Physical Science Text Book 1. Students will read the following topics on pages 464 and 466: Solar energy Geothermal Energy Other Renewal Source Conserving Energy Recourses 2. Students will complete Energy & Power worksheet #2.