1. 1 Momentum & Energy What is our definition of momentum? Momentum = mass x velocity Impulse? Impulse = Change in Momentum = Force x time What about Energy?

2. 2 Energy Demonstration Do you think this ball will hit his face? Where does the ball have the most energy? Where does it have the least energy?

3. 3 What is Energy? The universe is made up of Matter + Energy Matter is the substance Energy is the mover and changer of the matter

4. 4 Where does Energy come from? Energy comes from:  The sun Food Wind Water Energy can be: Light, heat, sound, electricity, radiation

5. 5 How do we measure Energy? Work = the amount of force needed to move an object a certain distance Work = force x distance What is this similar to? Impulse = force x time For both Work and Impulse, a force is applied and an object is moved!

6. 6 Work Work is done on an object only when an applied force moves it. No force = No momentum! No force = No work! No movement = No force

7. 7 CHECK YOURSELF Is work done when a weight lifter holds a barbell stationary above her head?

8. 8 Work Units Work = force x distance = Newtons x meters We call a Newton-meter the joule (J)

9. 9 Calculating Work Work = force x distance Example: A 100 N force is applied to move a 15 kg block a distance of 5 meters at a constant speed. How much work was done? 100 N x 5 m = 500 J

10. 10 Work & Power The definition of work says nothing about how long it takes to do the work. The same amount of work is done when carrying a load up a flight of stairs whether we walk or run. So why are we more tired after running upstairs in a few seconds than after walking up the same stairs?

11. 11 Power Power is the rate at which work is done Power = work done/time The time needed to run up the stairs is less than the time to walk, so the power for running is more!

12. 12 Power A high-power car engine does work quickly. An engine that delivers twice the power of another, however, does not necessarily move a car twice as fast or twice as far. Twice the power means that the engine can do twice the work in the same time.

13. 13 Power Units Power = work / time = Joules / seconds = Watts

14. 14 Calculating Power Power = work / time If given force, distance and time, then Power = (force x distance)/time

15. 15 Calculating Power - Example A new conveyor system at the local packaging plan will utilize a motor- powered mechanical arm to exert an average force of 890 N to push large crates a distance of 12 meters in 22 seconds. Determine the power output required of such a motor. Power= (890 N x 12 m) / 22 s = 485 Watts

16. 16 How are you feeling about this concept?  Reflection How well do you understand work? Power? Work & Power Calculations? What can you do to improve your understanding?