Question

A jogger's internal energy changes because he performs 6.80 105 J of work and gives off 4.9 105 J of heat. However, to cause the same change in his internal energy while walking, he must do 8.10 105 J of work. Determine the magnitude of the heat given off while walking.
J

Answer 1

decrease in U = work done + heat given off
=(6.8 +4.9)*10^5
= 11.7 * 10^5 J
then
11.7*10^5 = 8.1*10^5 + heat given off
heat given off = (11.7-8.1)10^5 = 3.6*10^5 J