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.

$t = 10 minutes; N = 33W; η = 6\%;$

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

$\eta=\dfrac{A_u}{A_f}\sdot100\%;$

$A_f = N ⋅ t; t =600 seconds ; A_f =33 ⋅ 600 = 19800J;$

$W = A_u =\dfrac{\eta\sdot A_f }{100\%};W =\dfrac{6\%\sdot 19800J }{100\%}=1188J;$

Answer:$W=1188J.$