Answer
(a) $106KPa$
(b) $42cm$
Work Step by Step
(a) The gas pressure inside the cylinder can be calculated as
$p=p_a+\frac{mg}{A}$
$\implies p=p_a+\frac{mg}{\frac{\pi}{4}r^2}$
We plug in the known values to obtain:
$p=101300+\frac{20(9.8)}{\frac{\pi}{4}(0.24)^2}$
$\implies p=105700Pa\approx 106KPa$
(b) We can determine the required height of the piston as follows;
$h_2=\frac{T_2}{T_2}h_1$
We plug in the known values to obtian:
$h_2=\frac{288}{576}(84cm)=42cm$
