1. Work and Power

2. WORK We now know that forces transfer energy. This process of energy transfer is called WORK. Work measures the effects of a force acting over a distance. When you are doing work you are transferring energy. This is why Work is measured in Joules (J)… it is the amount of energy transferred!!! W = F*d The units are N * m = Joules (J) (F)*(d) = (W)

3. Work Practice 1.) If you try to lift a car with 10N of force and it doesn’t move…How much work have you done? W = 0J 2.) A fireman applies 60N of force to turn on a water hydrant that rotates.05m. How much work was done? W = 3J 3.) You carry your 24N bookbag up 11m of stairs. How much work did you do? W = 264J

4. Power Running does not require more work than walking… so what is the difference between running and walking? A: The time it takes and the power!!! So we need to account for the time it takes to do work… the equation that measures that is Power: it equals the work done over time. P = W (Units for Power are J = Watts) t s

5. Power Running does not require more work than walking… so what is the difference between running and walking? Let’s prove it mathematically… Running Walking W = 100J W=100J t = 300s t = 600s P= ?W Use P = W/t to see if there is a difference in Power even though the SAME amount of WORK was done.

6. Power Running does not require more work than walking… so what is the difference between running and walking? Let’s prove it mathematically… RESULTS… Running = faster = less time = same work = MORE POWER!!! Walking = slower = more time = same work = LESS POWER!!!

7. Power Practice 1. While running track, Drew’s legs do 5780J of work in 183s. What is his power output? P = 31.58W 2. The chain that is pulling a rollercoaster up the first hill does 24652J of work over a 79s time interval. What is the power output of the chain? P = 312.05W 3. It takes Ms. Webb 20s to apply 23N of force to lift a box 5m. What was her power output? W = 115J so P = 5.75W