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Question
A car of mass 120 kg is moving at a speed 18 km/h and it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate:
- the work done by the engine.
- the power of the engine.
Solution
a. By work energy theorem
Work done = Change in K.E. of body
= `1/2"m"("v"^2-"u"^2)`
= `1/2xx120[(15)^2-(5)^2]`
= `1/2xx120[200]`
= 12000 J.
b. Power of engine = `"Work done"/"Time"`
= `12000/5`
= 2400 W
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