Work, Power and Energy • How much work so done to lift a 75 N bowling ball 1 meter? • W = Fd • W = (75 N) (1 m) = 75 J
Kinetic Energy of Motion • How much further will a car skid if you lock up the wheels at 90 km/h vs. 30 km/h? • EK = ½ mv2 • ½ mass x (90 km/h)2 = ½ mass x 8100 km2/h2 • ½ mass x (30 km/h)2 = ½ mass x 900 km2/h2 • ½ mass x 8100/ ½ mass x 900 = 9 • Nine times further!
Work, Power and Energy • What is the gravitational potential energy when a 75 N bowling ball has been lifted 1 meter? • EP = mgh • mg = weight = 75 N • EP = (75 N)(1 m) = 75 J • W = (75 N) (1 m) = 75 J
Work, Power and Energy • How much power is expended to lift a 75 N bowling ball 1 meter in 1 minute? • P = W/t • W = 75 J • P = (75 J)/60s = 1.25 W
Work, Power and Energy • How much power is expended to lift a 75 N bowling ball 1 meter in 1 second? • P = W/t • W = 75 J • P = (75 J)/1s = 75 W
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