1. Power The Crab Nebula, supernova remnant

2. Power Like work, we’ve all heard about power But what is it?

3. Scientists define power as the amount of work done divided by the time it takes to do that work Power is work’s rate of change Power = Work / Time

4. Definition #2 As work is related to energy, we can also define power as the rate of energy use Power = Change in Energy/Elapsed Time

5. Units The units of power are Joules/seconds 1J/s = 1 Watt (W) So if you lift your 1lb weight 10inches in the air in 1second, your power is 1watt

6. Power Comparisons Light Bulb: 100 W Vacuum Cleaner: 1,500 W Dodge Ram w/ Hemi: 250,000 W Space Shuttle: 11,000,000,000 W Sun: 400,000,000,000,000,000,000,000,000 W

7. Question A machine does 200J of work over a time interval of 20s. What is this machine’s power? 10W

8. How much Energy does a 40W light bulb consume in 2 minutes?

9. Machine A performs a certain amount of work in time t. Machine B performs twice as much work as 1, but takes 4 times as long. Machine C performs the same amount of work as 1, but in ½ the time. Rank the power of each machine in increasing order. 1.A, B, C2. C, B, A 3. C, A, B4. B, A, C 5. B, C, A

10. Using a 40N force, a pulley system pulls a box forward at a constant velocity of 2m/s. What is this pulley system’s power?