Question 164: Work, Energy and Power & Circular Motion

Question

A person trying to lose weight by burning fat lifts a mass of $$10$$ $$kg$$ upto a height of $$1$$ $$m$$ $$1000$$ 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 $$3.8 	imes {10^7}J$$ of energy per $$kg$$ which is converted to mechanical energy with a $$20\% $$  efficiency rate. Take $$g = 9.8\,m{s^{ - 2}}$$ :

Accepted Answer

Assume the amount of fat is used = x kg
So total Mechanical energy available through fat
= $$x 	imes 3.8 	imes {10^7} 	imes {{20} \over {100}}$$
And work done through lifting up
=  10 $$ 	imes $$ 9.8 $$ 	imes $$ 1000 = 98000 J
$$ \Rightarrow $$ $$x 	imes 3.8 	imes {10^7} 	imes {{20} \over {100}}$$ = 98000
$$ \Rightarrow $$ $$x$$ = 12.89 $$ 	imes $$ 10
-3
kg

Answer

$$9.89 	imes {10^{ - 3}}\,\,kg$$

Answer

$$12.89 	imes {10^{ - 3}}\,kg$$

Answer

$$2.45 	imes {10^{ - 3}}\,\,kg$$

Answer

$$6.45 	imes {10^{ - 3}}\,\,kg$$

Work, Energy and Power & Circular Motion

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