Question

an open water tight railway wagon of mass 5*10³kg coasts at an initial velocity of 1.2m/s without friction on a railway track. Rain falls vertically downwards into the wagon. What change occur in kinetic energy of wagon, when it has collected 10³ kg of water ?

Answer 1

$$\begin{gathered} Thekineticenergyofthewagon=\frac{1}{2}\times 5\times {10}^3\times 1.2\times 1.2=3.6\times {10}^{3}J \\ When{10}^{3}Kgofrainwateriscollectedinthewagonthen \\ K.E.=\frac{1}{2}\times 6\times {10}^3\times V{\text{'}}^2=3.6\times {10}^3 \\ orV{\text{'}}^2=1.2 \\ Thereforethereisnochangeinthekineticenergyofthewagon. \end{gathered}$$