The acceleration due to gravity on a planet is 1.96m/s. lf it is safe to jump from a height of 3m on the earth, then the corresponding height (in m) on the planet will be 

A person is safe, if his velocity while reaching the surface of moon from a height h is equal to its velocity while falling from height h on the earth.

So, $\sqrt{2{\mathrm{g}}^1{\mathrm{h}}^1}=\sqrt{2\mathrm{gh}}$

${\mathrm{h}}^1=\frac{\mathrm{gh}}{{\mathrm{g}}^1}=\frac{9.8\times 3}{1.96}=15 \mathrm{m}$