Question

A $50kg$ man is runing at a speed of $18km{h}^{-1}$. If all the kinetic energy of the man can be used to increase the temerature of water from ${20}^{0}C$ to ${30}^{0}C$, how much after can be heated with this energy?

Answer 1

The amount of energy required to raise the temperature is given by:

$E=ms\Delta \theta$

The kinetic energy of the person is

$KE=\frac{1}{2}m{v}^2$

Now, the kinetic energy of the man gets converted into heat energy.

$\frac{1}{2}M{v}^2=ms\Delta \theta$

$⟹m=\frac{M{v}^2}{2s\Delta \theta }$

$⟹m=\frac{50\times 5^2}{2\times 4.18\times 10}$

$⟹m=15g$