Answer
The height the ball was dropped is $1.36m$
Work Step by Step
The speed of the ball just before it hits the floor is: $$v=\frac{p}{m}=\frac{3.1}{0.6}=5.17m/s$$
We apply an equation of kinematics to find the height from which the ball was dropped.
We have the ball's initial velocity $v_0=0$ and final velocity $v_f=5.17m/s$; $g=9.8m/s^2$. So the height from which the ball was dropped is $$s=\frac{v_f^2-v_0^2}{2g}=1.36m$$
