1. Energy, Work, and Power

2. Some Definitions

3. Work= Force X Distance If a person exerts 20 Newtons of force to move 5 meters, he has done 100 Joules of work. W= 20N X 5m = 100 J

4. Solve this Problem: A ball weighing three Newtons falls a distance of 4 meters. What work has been done?

5. Work Done? a. A teacher applies a force to a wall and becomes exhausted. Explanation:______________________ _________________________________ _________________ Yes or No b. A weightlifter lifts a barbell over her head. Explanation:______________________ _________________________________ _________________ Yes or No c. A waiter carries a tray full of meals across the dining room at a constant speed. Explanation:______________________ _________________________________ _________________ Yes or No d. A rolling marble down hits a note card and moves it across a table. Explanation:______________________ _________________________________ _________________ Yes of No e. A shot-putter launches the shot. Explanation:______________________ _________________________________ _________________ Yes or No

6. Let's Practice! Tap the ball to reveal the assignment

7. Mechanical Advantage and Mechanical Efficiency Both ratios (fractions and percentages) show us how well the machine works.

8. Mechanical Efficiency--How well the machine uses the energy you put into it. It compares the work you do to the machine and the work you get out. The work you get out of the machine is always less than the work you put in and you lose some energy to friction. ME= work output work input X 100

9. Mechanical Advantage--How much force you get out of the machine. Your mechanical advantage should be greater than 1 for the machine to be useful. MA = Force output Force input

10. Attachments Practice Problems on Work.docx