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The mass of a cyclist together with the ...

The mass of a cyclist together with the bicycle is 90 kg. Calculate the work done by cyclist if the speed increase from 6 km/h to 12 km/h.

Text Solution

Verified by Experts

Mass of cyclist together with bike, m = 90 kg.
Initial velocity, u = 6 km/h = 6 `times` (5/18)= 5/3 m/s
Final velocity , v = 12 km/h `=12 times (15/8)=10/3` m/s
Initial kinetic energy `K.E_(I)=1/2mu^(2)-1/2(90)(5/3)^(2)=1/2(90)(5/3)(5/3)=125 J`
Final kinetic energy `K.E_(f) =1/2mv^(2)-1/2(90)(10/3)^(2)=1/2(90)(10/3)(10/3)=500 J`
The work done by the cyclist = change in kinetic energy
`=K.E_(f)-K.E_(I)=500 J-125J=375J`
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