Hydrostatics

Since the piston is circular, its area is given by πd2/4, where d is the diameter of the piston. Hence,

area = πd 2

4 = 0.0025

from which, d2 = 0.0025 × 4 π

= 0.003183

i.e. d = √0.003183 = 0.0564 m, i.e. 56.4 mm

Hence, the diameter of the piston is 56.4 mm.