Assuming that 20% of this goes into useful work and the other 80% is converted to heat, estimate the temperature rise of the body after 30 min if none of this heat is transferred to the environment. Express your answer using two significant figures.

The temperature rise of the body after 30 min is 1.0 °C.

Explanation:

The heat capacity of water is equal to one and it is the number of calories needed to raise the temperature of one gram by 1 degree celsius.                

     Cp = 1 cal/ g°C

(0.80)170 kcal/hr (1000 cal/kcal) (30 min) / 60 min/hr = 68000 cal.

68000 cal / 1 cal/ g°C / (70 kg (1000 g / kg)) = 1.0 °C.