When the ball is at height 31 cm it possess potential energy which is given as,
[tex]U=\text{mgh}[/tex]
When the ball rolls from height along the ruler the potential energy will be converted into kinetic energy.
According to conservation of energy,
[tex]K=U[/tex]
Plug in the known expression,
[tex]K=\text{mgh}[/tex]
Substitute the known values,
[tex]\begin{gathered} K=(45.93\text{ g)(}\frac{1\text{ kg}}{1000\text{ g}})(9.8m/s^2)(31\text{ cm)(}\frac{1\text{ m}}{100\text{ cm}})(\frac{1\text{ J}}{1kgm^2s^{-2}}) \\ \approx0.140\text{ J} \end{gathered}[/tex]
Thus, the kinetic energy of the ball is 0.140 J.
