Question

A stone is thrown vertically upwards with a velocity of 40m/s.

1.At what height will its knetic energy and potential energy be equal.

2.Calculate the P.E. of body if its mass=10 kg.

Answer 1

Given,
u=40 m/s
For maximum height,v=0 m/s
Using relation,
$$\begin{gathered} {\mathrm{v}}^2-{\mathrm{u}}^2=2\mathrm{gh} \\ 0-{40}^2=2\times (-10)\times \mathrm{h} \\ \mathrm{h}=80\mathrm{cm} \\ 1-\mathrm{Kinetic}\mathrm{energy}\mathrm{is}\mathrm{equal}\mathrm{to}\mathrm{potential}\mathrm{energy}\mathrm{at}\mathrm{h}\text{'}=\mathrm{h}/2=80/2=40\mathrm{cm} \\ 2-\mathrm{Potential}\mathrm{energy}\mathrm{of}\mathrm{body}\mathrm{of}\mathrm{mass}10\mathrm{kg}\mathrm{is}\mathrm{given}\mathrm{by} \\ \mathrm{P}.\mathrm{E}=\mathrm{mgh}=10\times 10\times 80=8000\mathrm{J} \end{gathered}$$