Question

Over the course of the day you do 1.5Mj of mechanical work and lose 28.5Mj of heat while maintaining a constant body temperature.

What mass of food with an energy content of 50 Mj kg -1 would you need to invest in order to avoid weight loss? (2sf and in kg)

Answer 1

Solution.

$A=1.5MJ;$

$\Delta U=28.5MJ;$

$W_1=50MJ/kg;$

$\Delta W=A+Q;$

$\Delta W=1.5MJ+28.5MJ=30MJ;$

$m=\dfrac{\Delta W}{W_1};$

$m=\dfrac{30MJ}{50 MJ /kg}=0.6kg;$

Answer: $m=0.6kg.$