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Question:

Grade 11 physics questions.?

A 50 kw motor in a crane lifts a mass of 4 tonnes througha eight of 10m in 20 secondsHow can I calculate the percentage of effiecieny of the motor if its working at full power?

Answer:

output energy mgh 4000x9.8x10 392000 joules power 392000 joules / 20s 19600 watts or 19.6 kW efficiency 19.6/50 39% assuming tonnes are metric tons4 tonnes 4000 kg .
output energy mgh 4000x9.8x10 392000 joules power 392000 joules / 20s 19600 watts or 19.6 kW efficiency 19.6/50 39% assuming tonnes are metric tons4 tonnes 4000 kg .

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