Answer
$D_{2}=1m$
Work Step by Step
According to Pascal's law:
$P_{1}=P_{2}$
$F_{1}=25kg*9.81\frac{m}{s^2}=245.25N$
$A_{1}=\frac{\pi*(10cm*\frac{1m}{100cm})^2}{4}=0.0025\pi m^2$
$P_{1}=\frac{245.25N}{0.0025\pi m^2}=\frac{98100}{\pi}Pa$
$F_{2}=2500kg*9.81\frac{m}{s^2}=24525N$
$A_{2}=\frac{\pi*(D_{2}(m))^2}{4}=0.25\pi*(D_{2}(m))^2$
$P_{2}=\frac{24525N}{0.25\pi*(D_{2}(m))^2}=\frac{98100}{\pi*(D_{2}(m))^2}Pa$
Then:
$\frac{98100}{\pi}Pa=\frac{98100}{\pi*(D_{2}(m))^2}Pa$.
Solving for $D$:
$D_{2}(m)=\sqrt \frac{9810\pi}{9810\pi}=1m$
