Area of narrow piston (A1) = 5 cm 2
Area of wider piston (A2) = 625 cm 2
force (F2) = 1250 N
{F_1\over A_1 } = {F_2\over A_2}⇒ {F_1\over 5 } = {1250\over 625}
⇒ {F_1} = {1250\over 625}×5 = 10 N
Hence, force acting on the smaller piston = 10 N
Assumption — There is no friction and no leakage of liquid.