Chapter 13: Work and Energy

1. Chapter 13: Work and Energy Pg. 416 The BIG idea: Energy is transferred when a force moves an object.

2. Section 1: Work is the use of force to move an object. Section 2: Energy is transferred when work is done. Section 3: Power is the rate at which work is done.

3. New (and not so new) Vocabulary • Work • Joule • potential energy • kinetic energy • mechanical energy • conservation of energy

4. Take notes in your interactive notebook on pg. 40. Write “Chapter 13, Section 1” at the top of your page. Under that, write “Notes”

5. Force is necessary to do work • Work: in science is defined as using force to make an object MOVE. • If the object doesn’t move, you have not done any work (think of holding up the book). • A force is a push or a pull. • Work is only done by the force that acts in the same direction that the object is moving.

6. Work can be calculated using the formula W = F x d. Force is measured in Newtons, distance is measured in meters. • One Newton x 1 meter = 1 Joule.

7. Let’s work a sample problem together: How much work is done if a person lifts a barbell weighing 450 N a height of 2 m? What do we have to calculate? work What formula will we use? W = F x d What is given? F = 450 N d = 2 m (450 N) (2m) W= W = 900 Nm or 900 J

8. Now it’s your turn! On the same page of your interactive notebook as your notes, work the two “Practice the Math” problems on the bottom of pg. 421. When you finish BOTH PROBLEMS, raise your hand so someone can check the answers for you.

9. BIG IDEA Energy is transferred when a force moves an object. KEY CONCEPT Work is the use of force to move an object 1. Force is necessary to do work. Work is the use of force to move an object a certain distance. You can calculate work if you know the force and the distance over which it is applied. If you exert a force of 20 N as you push your desk 3 m across the floor of your bedroom, how much work have you done? Show the work you do to solve the problem. W = f x d W = 20 N x 3 m W = 60 N x m W = 60 J

10. 2. Objects that are moving can do work. Look at the scene below. On the blank lines, describe how each object is doing work. wind does work on the leaves moving wind does work on the sailboat the mallet does work on the croquet ball Gravity does work on the child

11. http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_pg113_work/mfm05_pg113_work.htmlhttp://www.classzone.com/books/ml_science_share/vis_sim/mfm05_pg113_work/mfm05_pg113_work.html

12. http://www.brainpop.com/science/motionsforcesandtime/work/