question_answer

How fast should a man of mass 50 kg run, so that his kinetic energy be 625 J?

Answer:

Given,   \[m=50JK.E.=625J\]                 \[v=?\] We know, \[K.E.=\frac{1}{2}m{{v}^{2}}\] \[\Rightarrow {{V}^{2}}=\frac{2\times K.E.}{m}\] \[\Rightarrow V=\sqrt{\frac{2\times K.E.}{m}}\] \[\therefore V=\sqrt{\frac{2\times 625}{50}}=\sqrt{25}=5m/s\]