Power Contents Definition of Power Whiteboards Jambalaya Whiteboards

Power Contents: • Definition of Power • Whiteboards • Jambalaya • Whiteboards

Power - The rate at which work is done Power = Work/Time P = W/ t • P = Power • W - Work done • t - Time to do work A person does 145 J of work in 20. 0 s. What is power output? P = W/ t = (145 J)/(20. 0 s) = 7. 25 J/s = 7. 25 Watts = 7. 25 W 1 horsepower = 745. 7 Watts, 1 k. W = 1000 Watts

Power - The rate at which work is done power = work/time = (Fd)/t = F(d/t) = Fv • F = Force to move something • v = Velocity it is moving P = Fv My 30. HP van could go 25 m/s top speed. What was the force resisting its motion? 1 horsepower = 745. 7 Watts, 1 k. W = 1000 Watts power = (30 HP)(745. 7 Watt/HP) = 22, 371 W P = Fv 22, 371 W = F(25 m/s), F = 890 N

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Joe Mama does 613 J of work in 2. 13 seconds. What is his power output? P = W/ t = (613 J)/(2. 13 s) = 288 W

Ima Wonder can put out 127 W of power. What time will it take her to do 671 J of work? P = W/ t, t = W/P = (671 J)/(127 W) = 5. 28 s

What work does a 1. 5 HP motor do in 1 minute? P = (1. 5 HP)(745. 7 W/HP) t = 60 s P = W/ t, W = Pt = (1118. 55 W)(60 s) = 67113 J 67, 000 J

Bob N. Frappels slides a box with 43 N of force at a constant speed of 5. 3 m/s. What is his power output? P = Fv = (43 N)(5. 3 m/s) = 227. 9 W = 230 W

Frieda People can put out 430 W of power. With what speed can she push a car if it takes 152 N to make it move at a constant velocity? P = Fv v = P/F = (430 W)/(152 N) = 2. 83 m/s

Power all mixed up Formulas: F = mg (Lifting) F = mg (Dragging) P = W/t (Power) W = Fd (Work) It’s a Things we can know P - Power (in W) W - Work (in J) F - Force (in N) d - distance (in m) t - time (in s) m - mass (in kg) - coefficient of friction Jambalaya!

Formulas: F = mg (Lifting) F = mg (Dragging) P = W/t (Power) W = Fd (Work) P - Power (in W) W - Work (in J) F - Force (in N) d - distance (in m) t - time (in s) m - mass (in kg) - coefficient of friction Sample 1 - A 840 W winch can lift a 2350 kg Land Rover up 8. 2 m into a tree in what time?

Formulas: F = mg (Lifting) F = mg (Dragging) P = W/t (Power) W = Fd (Work) P - Power (in W) W - Work (in J) F - Force (in N) d - distance (in m) t - time (in s) m - mass (in kg) - coefficient of friction Sample 2 - Gumi Baere drags a 45. 1 kg box that has a coefficient of friction between it and the floor of 0. 34 a distance of 16 m in 11. 7 seconds. What is her power output?

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What must be the power rating of a motor if it is to lift a 560 kg elevator up 3. 2 m in 1. 5 seconds? F = mg = (560 kg)(9. 8 N/kg) = 5488 N W = Fd = (5488 N)(3. 2 m) = 17561. 6 J P = W/t = (17561. 6 J)/(1. 5 s) = 11707. 7 W 11700 W

A 560. W winch can lift a car 5. 2 m in 37 seconds. What must be the mass of the car? 1 HP = 745. 7 W P = W/t, W = Pt = (560 W)(37 s) = 20, 720 J W = Fd, F = W/d = (20, 720 J)/(5. 2 m) = 3984. 6 N F = mg, m = F/g = (3984. 6 N)/(9. 8 N/kg) = 406. 6 kg 407 kg

Red Elk leads a dog team that can put out 2. 5 k. W of power. They skid a 312 kg sled a distance of 340 m in 93 seconds. What must be the coefficient of friction? P = 2500 W P = W/t, W = Pt = (2500 W)(93 s) = 232500 J W = Fd, F = W/d = (232500 J)/(340 m) = 683. 8 N F = mg, = F/(mg) = (683. 8 N)/((312 kg)(9. 8 N/kg)) . 22 =. 22

A 150 HP tractor can drag a 350 kg load how far in a minute if the coefficient of friction between the load and the ground is 0. 78. 1 HP = 745. 7 W P = (150 HP)(745. 7 W/HP) = 111855 W F = mg = (. 78)(350 kg)(9. 8 N/kg) = 2675. 4 N P = W/t, W = Pt = (111855 W)(60 s) = 6711300 J W = Fd, d = W/F = (6711300 J)/(2675. 4 N) = 2508 m 2500 m