Work Power and Energy 5 Question 3

5. A person trying to loose weight by burning fat lifts a mass of 10kg upto a height of 1m1000 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 3.8×107J of energy per kg which is converted to mechanical energy with a 20 efficiency rate. (Take, g=9.8ms2 )

(2016 Main)

(a) 2.45×103kg

(b) 6.45×103kg

(c) 9.89×103kg

(d) 12.89×103kg

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Answer:

Correct Answer: 5. (d)

Solution:

  1. Work done in lifting mass =(10×9.8×1)×1000

If m is mass of fat burnt, then energy

=m×3.8×107×20100

Equating the two, we get

m=493.812.89×103kg



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