Question

A ball is dropped from a height of 40 cm. It hits the ground and rebounds back to a height of 20cm. What will be thw percentage loss of energy?
a)50%
b)40%
c)60%
dnone of these
e) 0%

Answer 1

$$\begin{gathered} \mathbf{Potential}\mathbf{}\mathbf{energy}\mathbf{:} \\ \mathrm{PE}=\mathrm{mgh} \\ \frac{{\mathrm{E}}_2}{{\mathrm{E}}_1}=\frac{{\mathrm{mgh}}_2}{{\mathrm{mgh}}_1} \\ =\frac{{\mathrm{h}}_2}{{\mathrm{h}}_1} \\ =\frac{20}{40} \\ =\frac{1}{2} \\ {\mathrm{E}}_2=\frac{{\mathrm{E}}_1}{2}=50\%\mathrm{of}{\mathrm{E}}_1 \\ \mathrm{Hence},\mathrm{the}\mathrm{energy}\mathrm{loss}\mathrm{is}\mathrm{equal}\mathrm{to}50\%. \\ \mathbf{Ans}\mathbf{:}\mathbf{}\mathbf{Option}\mathbf{}\mathbf{-}\mathbf{}\mathbf{a} \end{gathered}$$