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A person trying to lose weight by burnin...

A person trying to lose weight by burning fat lifts a mass of 10 kg up to a height of 1m 1000 times.
Assume that the potential energy lost each time he lowers the mass is dissipated.
How much fat will he use up considering the work done only when the weight is lifted up ? Fat supplies `3.8xx10^7J` of energy with a 20% effciency rate.Take `g=9.8m//s^2`

A

`2.45xx10^(-3)`kg

B

`6.45xx10^(-3)`kg

C

`9.89xx10^(-3)`kg

D

`12.89xx10^(-3)`kg

Text Solution

Verified by Experts

The correct Answer is:
D
Loss of potential energy
`=mgh xx1000 =10xx9.8xx1xx1000=9.8xx10^4j`
If fat of mass m is dissipated, then mechanical energy obtained
`=mxx3.8xx10^7xx(20)/(100)=mxx0.76xx10^7J`
According to the equestion,
`mxx0.76xx10^7=9.8xx10^4`
`therefore m=(9.8xx10^4)/(0.76xx10^7)=12.89xx10^(-3)`kg
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