A ball falls vertically downward and bounces off a horizontal floor. The speed of the ball just before reaching the floor $\left(\mathrm{u}_{1}\right)$ is equal to the speed just after having contact with the floor $\left(\mathrm{u}_{2}\right) ; \mathrm{u}_{1}=\mathrm{u}_{2} .$ The corresponding magnitudes of accelerations are denoted respectively by $a_{1}$ and $a_{2} .$ The air resistance during motion is proportional to speed and is not negligible. If $g$ is acceleration due to gravity, then-