Question

your walk to your morning physics lecture takes 10 minutes and as you walk you do mechanical work at a rate of 33W with an efficiency of 6%. How much energy stored in your body ahve you used up over the course of your walk?

Answer 1

Solution.

t = 10 minutes =600 seconds ;

N = 33W;

$\eta$ = 6 %;

The efficiency ratio is the ratio of useful work to full work multiplied by 100%:

$\eta$ = (A_useful/ A_full)$\sdot$ 100%;

A_full = N $\sdot$ t;

A_full =33W $\sdot$ 600 seconds = 19800J;

W = A_useful = ($\eta$$\sdot$ A_full)/100%;

W = (6 % $\sdot$ 19800J)/100% = 1188 J;

Answer: W = 1188 J.