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Published byJoel Holland Modified over 9 years ago
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Work and Power
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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)
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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
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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
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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.
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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!!!
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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
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