Chapter 15 Energy Assignments 15.1 Math Skills 1-3 p 448; AQs 1-9 p452

15.1 Learning Targets for Energy and its Forms Describe the relationship between work and energy Calculate the kinetic energy of an object given the objects mass and velocity Analyze how potential energy is related to an object’s position and give examples of gravitational and elastic potential energy Solve equations that relate an object’s gravitational potential energy to its mass and height Give examples of the major forms of energy

MP 1. A 70. 0-kilogram man is walking at a speed of 2. 0 m/s 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 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

18,000 J = 25*v2 (divide both sides by 25) 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

2. How is the kinetic energy of an object determined? KE = ½ m*v2

3. What factors determine the gravitational potential energy of an object? 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

5. When you heat a pot of water over a flame, what form of energy is added to the water? Thermal

6. Applying Concepts  What kind of energy is represented by an archer stretching a bow string? Elastic potential energy

Yes, KE & PE are not mutually exclusive E.g. a falling leaf 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

PE = m*g*h PE = 60.0 kg*9.8m/s/s*74.8m PE = 44,000 J 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 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