We go out to sunbathe on a warm summer day If we soak up 100

We go out to sunbathe on a warm summer day. If we soak up 100 British thermal units [BTU] per hour of energy, how much will the temperature of a 132 pound-mass person increase in 2 hours, in units of degrees Celsius? We can assume that since our bodies are mostly water, they have the same specific heat as water.

Solution

1 BTU = 1055 Joules (Conversion Factor)

Heat absorbed by body in 2 hours = 2 * 100 BTU = 200 BTU * 1055 Joules/BTU = 211000 J

Heat required is used to increase the temperature of the human body

1 pound = 0.453592 Kg

132 pound = 59.8742 Kg = 59874.2 gms

Heat = mass * specific heat of water * Change in temperature

211000 = 59874.2 * 4.184 J/gC * Change in temperature

Change in temperature = 0.8422C

Hence there is a rise of 0.8422C in the body temperature