Step 1: Use Pascal's law.
In a hydraulic lift, pressure applied at one piston is transmitted equally throughout the liquid.
Therefore,
\[
\frac{F_1}{A_1}=\frac{F_2}{A_2}
\]
where \(F_1\) is the force on piston \(P_1\), \(F_2\) is the force on piston \(P_2\), and \(A_1,A_2\) are their respective areas.
Step 2: Calculate the force on piston \(P_1\).
A body of mass
\[
m=2\,\text{kg}
\]
is placed on piston \(P_1\).
So the force on \(P_1\) is its weight:
\[
F_1=mg
\]
\[
F_1=2\times 10
\]
\[
F_1=20\,\text{N}
\]
Step 3: Calculate the ratio of areas.
The radius of piston \(P_1\) is
\[
r_1=2\,\text{m}
\]
and the radius of piston \(P_2\) is
\[
r_2=8\,\text{m}.
\]
Since area of a circular piston is
\[
A=\pi r^2,
\]
we get
\[
\frac{A_2}{A_1}
=
\frac{\pi r_2^2}{\pi r_1^2}
\]
\[
=
\frac{8^2}{2^2}
\]
\[
=
\frac{64}{4}
\]
\[
=16
\]
Step 4: Find the force on piston \(P_2\).
From Pascal's law,
\[
F_2=F_1\frac{A_2}{A_1}
\]
\[
F_2=20\times 16
\]
\[
F_2=320\,\text{N}
\]
Step 5: Final conclusion.
Therefore, the force on piston \(P_2\) is
\[
\boxed{320\,\text{N}}
\]