[tex]v=2\ m/s\\\\E_k=16\ J=16\ \frac{kgm^2}{s^2}\\\\E_k=\frac{mv^2}{2}\\\\\frac{m\cdot(2\ m/s)^2}{2}=16\ \frac{kgm^2}{s^2}\\\\\frac{m\cdot4\ m^2/s^2}{2}=16\ \frac{kgm^2}{s^2}\\\\2m\ m^2/s^2=16\ \frac{kgm^2}{s^2}\ \ /:2\ m^2/s^2\\\\m=8\ kg-answer[/tex]
