1. Power
In which situation would you tire more quickly?

2. Power

3. Notice that in the formula for work, it says nothing about time
WORK = FORCE X DISTANCE

4. THE RATE AT WHICH WORK IS DONE
Power
THE RATE AT WHICH WORK IS DONE
POWER = WORK DONE
TIME
UNIT: JOULE
SECOND
: WATT

5. Pit Pony

6. A little bit of history
To find out how the power of his engine compared to that of a horse, James Watt measured how fast an average horse could do work. He found the answer and expressed the amount of work performed per second as a horsepower.
A horse exerting 1 horsepower can raise 330 pounds of coal 100 feet in a minute.
In the US we rate engines in terms of horsepower (hP) and electricity in watts (kilowatts, megawatts)

7. 1 horsepower= 746 watts

8. What can a more powerful engine do?
ONE OF 2 THINGS
POWER = WORK DONE
TIME
2X WORK OR WORK
TIME ½ TIME

9. Practice Calculate the work done by both of you.
You and your friend are getting paid by your neighbor to move N piles of soil to a garden that is 100 m away. You accomplished the task in 10 minutes, but your friend took 30 minutes.
Calculate the work done by both of you.
2) Calculate the Power for each of you.

10. Practice
A small motor runs a ski lift that pulls a group of children weighing 836 N to a height of 10.7 m in 23.2 s. What is the minimum power the motor must produce?
386 Watts

11. Practice
You are helping your dad reshingle the roof. You carry 306 kg of shingles up the roof 7 meters from the ground in 1200 seconds. Calculate your power.
17.5 Watts

12. The second formula for power is...
Power = Work = F•d =
Time t
A wagon weighing 1800 N is pulled by a horse at a speed of 0.40 m/s. What is the power of this horse?
720 Watts