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A person trying to lose weight lifts a 1...

A person trying to lose weight lifts a 10 kg mass, one thousand times, to a height of 0.5m each time. Assume that the P.E. lost each time the person lowers the mass is dissipated.
How much work does the person do against the gravitational force?

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Verified by Experts

Given `m=10kg,g=9.8ms^(-2),h=0.5m,n=1000`
Energy supplied by fat is `3.8xx10^(7)J//kg`, efficiency = 20%
`therefore20%` of energy supplied by fat = `3.8xx10^(7)xx0.20=0.76xx10^(-7)Jkg^(-1)`
Work done against the gravity = n mgh = `10^(3)xx10xx9.8xx0.5=4.9xx10^(4)J`
Mass of fat used = `(4.9xx10^(4))/(0.76xx10^(7))=6.45xx10^(-3)kg`
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