1. W ORK AND P OWER

2. W ARM U P 1. Which of the liquids in the graduated cylinder below is the least dense? 2. Which is the most dense? 3. Estimate the density of Liquid C. 4. Calculate the density of a metal block with a mass of 40 grams and a volume of 5 milliliters.

3. B RAIN P OP : W ORK

4. W HAT IS WORK ? Work is done when a force causes an object to move in the direction of the force. The force and the direction of movement must be parallel Always involves a transfer of energy work not work

5. Applying a force doesn’t always mean that work is done. Example: if you push against a wall for an hour, and it doesn’t move, you haven’t done work

6. ExampleDirection of force Direction of motion Doing work? Pushing a box Walking with your backpack on Lifting a bag of groceries Carrying a bag of groceries

8. Work = force x distance Force applied to an object (in newtons) Distance the object moves (in meters) Work is measured in Joules (like energy)

9. Path 1: exert less force over a longer distance Path 2: exert more force over a shorter distance Same amount of work done for each path

11. E UREKA : W ORK http://www.youtube.com/watch?v=xBnS23U_ao4

13. B RAIN POP POWER Quiz

14. I S WORK HAPPENING ? Lifting a weight a distance of 2 meters

15. I S WORK HAPPENING ? Holding a weight still over your head for 2 hours

16. W ORK, E NERGY, AND P OWER IN H OCKEY http://science360.gov/obj/video/c5be5456-2e39- 49a7-8118-218868df89eb/work-energy-power

17. B UZZER BEATER 1. What is the formula and unit for work? 2. What is the formula and unit for power? 3. A force of 15 N is exerted over a distance of 6 m. How much work was done? A21 J B21 N C90 J D90 N 4. If 350 J of work was done in 50 s, what was the power output? F7 W G70 W H1,750 W I17,500 W