Work, Energy, and Power



Work, Energy, and Power

GO to: and answer the following Questions. Drop your final product in Mr. Falls’s Dropbox.

Part One

1. Define Work

2. What are the three key words in the definition above?

3. What must there be in order for a force to qualify as doing work on an object?

4. Read the five examples and check your answers.

5. What is the equation for work?

6. What does the angle theta represent?

7. Look at scenarios A,B, and C. Why is the work done by the waiter on the tray zero?

8. Look at the diagram of Fido. Which component of the tension force F causes Fido to be displaced? Why? How can you calculate this component?

9. What is the standard unit of work? What is it equivalent to?

10. What 3 quantities must be known to calculate work?

11. Go through examples 1-9 and check your answers and take notes as you go.(you might see some of these again on a quiz!)

12. What is potential energy?

13. List the two types of potential energy we will discuss in this class.

14. What 2 things does gravitational potential energy depend on?

15. What is the equation for gravitational potential energy?

16. Go through the example of the balls at various heights and check your answer. Where you correct? If not were did you make your mistake?

17. What is elastic potential energy?

18. Give at least four ways that elastic potential energy can be stored.

19. What 2 things does the force required to compress or stretch a spring a certain distance depend on?

20. What is the equation for this force?

21. What is the equilibrium position of a spring?

22. How can you calculate the elastic potential energy of a spring?

23. When does an object possess elastic potential energy.

24. Do check your understanding 1 and 2. How does the work done to push the cart up the ramp compare to the cart’s change in potential energy?

Part 2

1. What is kinetic energy?

2. List three forms of kinetic energy.

3. What 2 things does translational kinetic energy depend on?

4. What is the equation for translational kinetic energy?

5. If you triple an object’s speed, what happens to its kinetic energy?

6. What kind of a quantity is kinetic energy? What are its units?

7. Go through check your understanding 1-4 and check your answers. Describe how you would solve #4.

8. What is the energy acquired by an object on which work is being done?

9. What are the two forms of mechanical energy?

10.List at least four examples of objects with mechanical energy, the form of the energy, and the cause(i.e. what the energy is due to).

11. When one object does work on another object, what gets exchanged?

12. Describe how a pile driver is able to do work. In each of the three pictures what is the form of the mechanical energy?

13. Describe how a dart gun is able to do work on a dart.

14. What is the total mechanical energy of an object?

15. Look at the diagram of the Chinese Ski Jumper. What do you notice about the sum of the kinetic and potential energy at each point?

Part 3 Power

1. Does work depend on the time that a force acts on an object?

2. Define power. What is the equation for power?

3. What unit is power measured in?

4. What is the unit of power equivalent to?

5. What are most machines built to do?

6. How are they described?

7. Give another equation for power that involves velocity.

8. What does this new expression reveal about a powerful machine?

9. Go through the check your understanding problems and check your answers.

Part 4 The Work-Energy Theorem

1. Give two examples of internal forces and 3 examples of external forces.

2. What happens when work is done on an object by an external force?

3. What happens when work is done on an object by an internal force?

4. What happens when the only forces doing work are internal forces?

5. Go through the five descriptions of motion.

6. When is positive work done on an object by an external force? What happens to the object’s mechanical energy?

7. When is negative work done on an object by an external force? What happens to the mechanical energy now?

8. Give an equation that relates total mechanical energy and work.

9. Rewrite the above equation using PE and KE.

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