A person trying to lose weight (dieter ) lifts a 10 kg mass through 0.5m, 1000 times, A ssume that the potential energy lost each time she lowers the mass is dissipated (a) How much work does she does against the gravitational force ? (b) Fat supplies `3.8xx10^(7) J` of energy per kilogram which is converted to mechanical energy with a `20%` efficiency rate. How much fat will the dieter use up ?

A person trying to lose weight (dieter ) lifts a 10 kg mass through 0.

1.	A person trying to lose weight (dieter ) lifts a 10 kg mass through 0.5m, 1000 times, A ssume that the potential energy lost each time she lowers the mass is dissipated (a) How much work does she does against the gravitational force ? (b) Fat supplies `3.8xx10^(7) J` of energy per kilogram which is converted to mechanical energy with a `20%` efficiency rate. How much fat will the dieter use up ?
Answer» Here, `m=10kg, h=0.5m, n=1000` (a) Work done against gravitational force `W=n(mgh)=1000xx(10xx9.8xx0.5)=49000J.` (b) Mechanical energy supplied by 1 kg of fat `=3.8 xx10^(7)xx(20)/(100)=0.76xx10^(7)J//kg` `:.` Fat used up by the dieter `=(1kg)/(0.76xx10^(7))xx49000=6.45xx10^(-3)kg`

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