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Power

Power. Power. T he rate of doing work or transforming energy. Calculating Power. P = W or P = ∆E ∆t ∆t W – work (J) ∆E – energy (J) ∆t – time (s) P – Power (Watts (W) or J/s)

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Power

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  1. Power

  2. Power The rate of doing work or transforming energy.

  3. Calculating Power P = W or P = ∆E ∆t ∆t W – work (J) ∆E – energy (J) ∆t – time (s) P – Power (Watts (W) or J/s) NOTE: W is both the variable representing work and representing the units of power, watts. Be sure not to get them confused!

  4. Example 1 The left ventricle of the human heart has an average of 3.0 W of power. How much work does your heart do in half an hour? Ans: 5.4x102 J

  5. Example 2 Fatheen goes on “Launch”, the new ride at Canada’s Wonderland. During the ride, Fatheen rises 30 m in 10 s. If Fatheen weighs 80 kg, calculate: a) the work done by the ride? b) the power of “Launch”? Ans: a) W = 2.4 x 104J b) P = 2.4 x 103 W

  6. Practice 1. The motor on a rollercoaster can lift the train cars filled with people (12500 kg) to the top of the first hill (38.5 m) in 22 seconds. Determine the power output of the motor. 2. How much energy does a 60 W incandescent light bulb use in 1 hour? How long would it take a 15 W florescent light bulb to use the same amount of energy? 3. An elevator motor produces 2,000 W. How fast (in m/s) can it lift a 1,000-kg load? 4. A car must do work at a rate of 10 kW to maintain a constant speed of 25 m/s on flat ground. How large are the forces opposing its motion?

  7. Heads Up Tomorrow you will be coming up with your own Power lab and completing a formal lab write-up. Think about what you might want to find the power of! It should be SIMPLE and use only students and equipment readily available at school.

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