A vehicle (mass=1000 kg) , moving at a speed of $\;36 \;kmh^{-1}\;$ is stopped in 2 s . Assuming that $\;50 \%\;$ of the mechanical energy lost appears as thermal energy , the average rate of production of thermal energy in $\;cal s^{-1}\;$ is -

Question

$(a)\;2 \times 10^{3} \;cals^{-1}\qquad(b)\;3 \times 10^{3} \;cals^{-1}\qquad(c)\;4 \times 10^{3} \;cals^{-1}\qquad(d)\;5 \times 10^{3} \;cals^{-1}$