Question

How fast should a man weighing 500 N run so that his kinetic energy is 900 J? ($g=10m{s}^{-2}$)

Answer 1

Mass of the man $m=\frac{W}{g}=\frac{500}{10}=50kg$

Kinetic energy $K.E=\frac{1}{2}m{v}^2$

Or $900=\frac{1}{2}\times 50\times v^2$

$⟹v=6m/s$