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A person trying to lose weight by burning fat lifts a mass of 10 kg upto 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 3.8 × 10⁷ J of energy per kg which is converted to mechanical energy with a 20% efficiency rate. Take g = 9.8 m s⁻²:

1. 2.45 × 10⁻³ kg
2. 6.45 × 10⁻³ kg
3. 9.89 × 10⁻³ kg
4. 12.89 × 10⁻³ kg

Correct answer: 12.89 × 10⁻³ kg

Solution

The correct option is right because the total work done in lifting the mass is calculated, and considering the efficiency of energy conversion, the amount of fat used is derived from the energy required to perform that work. The calculations show that the energy expended corresponds to approximately 12.89 grams of fat.

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