
$a v _{1}=\frac{ a }{2} v _{2}$
$v _{2}=2 v _{1}$
From Bernoulli's theorem,
$P _{1}+\rho g h_{1}+\frac{1}{2} \rho v _{1}^{2}= P _{2}+\rho g h_{2}+\frac{1}{2} \rho v _{2}^{2}$
$P _{1}- P _{2}=\rho\left[\left(\frac{ v _{2}^{2}- v _{1}^{2}}{2}\right)+ g \left( h _{2}- h _{1}\right)\right]$
$4100=800\left[\left(\frac{4 v _{1}^{2}- v _{1}^{2}}{2}\right)+10 \times(0-1)\right]$
$\frac{41}{8}+10=\frac{3 v _{1}^{2}}{2}$
$\frac{121}{8} \times \frac{2}{3}= v _{1}^{2}$
$v _{1}=\sqrt{\frac{ I 21}{4 \times 3} \times \frac{3}{3}}$
$v _{1}=\frac{\sqrt{363}}{6} \; m / s$
$X =363$

(Take acceleration due to gravity $=10\,ms ^{-2}$ )
[Given: $\pi=22 / 7, g=10 ms ^{-2}$, density of water $=1 \times 10^3 kg m ^{-3}$, viscosity of water $=1 \times 10^{-3} Pa$-s.]
$(A)$ The work done in pushing the ball to the depth $d$ is $0.077 J$.
$(B)$ If we neglect the viscous force in water, then the speed $v=7 m / s$.
$(C)$ If we neglect the viscous force in water, then the height $H=1.4 m$.
$(D)$ The ratio of the magnitudes of the net force excluding the viscous force to the maximum viscous force in water is $500 / 9$.