The radius of the cylindrical iron piece \( (r) = \cfrac{5.6}{2}\) cm \(=2.8\) cm, and its height \((h) = 5\) cm.
∴ The volume of the cylindrical iron piece
\(=πr^2 h\) cubic cm \(=π×(2.8)^2×5\) cubic cm.
The radius of the gas jar \(=\cfrac{7}{2}\) cm.
Let the rise in the water level be \(x\) cm.
∴ According to the condition, \(π×(\cfrac{7}{2})^2 x=π×(2.8)^2×5 \)
or, \(\cfrac{49x}{4}=\cfrac{28×28×5}{10×10} \)
or, \(x=\cfrac{28×28×5×4}{10×10×49} \)
or, \(x=3.2\)
∴ The water level in the gas jar will rise by \(3.2\) cm.