Chapter 15

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# Chapter 15 - PowerPoint PPT Presentation

Chapter 15. Energy Assignments 15.1 Math Skills 1-3 p 448; AQs 1-9 p452 15.2 Math Skills 1-3 p 458; AQs  1-6 & 9-10. 15.1 Learning Targets for Energy and its Forms. Describe the relationship between work and energy

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### Chapter 15

Energy Assignments

15.1 Math Skills 1-3 p 448; AQs 1-9 p452

15.2 Math Skills 1-3 p 458; AQs  1-6 & 9-10

15.1 Learning Targets for Energy and its Forms
• Describethe relationship between work and energy
• Calculate the kinetic energy of an object given the objects mass and velocity
• Analyzehow potential energy is related to an object’s position andgive examples of gravitational and elastic potential energy
• Solve equations that relate an object’s gravitational potential energy to its mass and height
• Give examplesof the major forms of energy
MP 1.A 70.0-kilogram man is walking at a speed of 2.0 m/s. What is his kinetic energy?
• KE = ½ m*v2
• KE = 0.5 * 70.0 kg * (2.0 m/s)2
• KE = 0.5 * 70.0 kg * 4.0 m/s
• KE = 140 J
MP 2.A 1400-kilogram car is moving at a speed of 25 m/s. How much kinetic energy does the car have?
• KE = ½ m*v2
• KE = 0.5 * 1400 kg * (25 m/s)2
• KE = 0.5 * 1400 kg * 625 m/s
• KE = 437,500 J

MP 3.A 50.0-kilogram cheetah has a kinetic energy of 18,000 J. How fast is the cheetah running? (Hint: Rearrange the equation to solve for v.)

• KE = ½ m*v2
• 18,000 J = 0.5*50.0 kg*v2
• 18,000 J = 25*v2 (divide both sides by 25)
• 720 J = v2 (take the square root of both sides)
• v = 26.8 m/s
1. Describe the relationship between work and energy.
• Energy is the ability to do work, and work is the transfer of energy
• Its mass
• The acceleration due to gravity
• Its height
• PE = m*g*h
4. Give an example of each of the major forms of energy.
• Chemical – wood, gasoline
• Electrical – ipod
• Mechanical – bouncing ball
• Electromagnetic – light
• Nuclear – nuclear power plants
• Thermal – molten steel, fire
6. Applying Concepts  What kind of energy is represented by an archer stretching a bow string?
• Elastic potential energy
7. Applying Concepts  Can an object have both kinetic energy and potential energy at the same time? Explain
• Yes, KE & PE are not mutually exclusive
• E.g. a falling leaf

8. A 60.0-kg person walks from the ground to the roof of a 74.8-m-tall building. How much gravitational potential energy does she have at the top of the building?

• PE = m*g*h
• PE = 60.0 kg*9.8m/s/s*74.8m
• PE = 44,000 J
9. A pitcher throws a 0.145 kg-baseball at a velocity of 30.0 m/s. How much kinetic energy does the ball have?
• KE = ½ m*v2
• KE = 0.5*0.145 kg*(30.0 m/s)2
• KE = 0.5*0.145 kg*900 m/s
• KE = 65.3 J