Question

A 61.8-kg runner produces 279 J of energy per second while running a marathon. Assuming 11.3% of the energy is delivered to the muscle tissue and that the excess energy is removed from the body by evaporation of sweat, determine the mass of bodily fluid (assume it is water) lost per hour.

Answer 1

Answer:

The mass of bodily fluid lost per hour is 0.369 kg

Explanation:

Mass of runner $m = 61.8$ kg

Energy produced by the body $E = 279$ J

Here 11.3% of energy is delivered to the muscle tissue, that implies 88.7% of this energy used to evaporate the sweat as heat.

Heat energy used in one hour is

  $Q = 279 \times 0.887 \times 3600$

  $Q = 8.9 \times 10^{5}$ $\frac{J}{hr}$

From the formula of latent heat,

   $Q = L_{V} m$

Where $L_{V} = 2.41 \times 10^{6}$ $\frac{J}{kg}$      ( Latent heat of vaporization for water )

   $m = \frac{Q}{L_{V} }$

   $m = \frac{8.9 \times 10^{5} }{2.41 \times 10^{6} }$

   $m = 0.369$ kg

Therefore, the mass of bodily fluid lost per hour is 0.369 kg