A child wants to pump up a bicycle tire so that its pressure is 1.2 * 105 pa above that of atmospheric pressure. if the child uses a pump with a circular piston 0.035 m in diameter, what force must the child exert?

General expression is;

Pressure = Force/Area

In which,

Pressure = Required pressure + Atmospheric pressure = (1.2*10^5) + (101325) = 221325 Pa = 221325 N/m^2

Area = πD^2/4 = π*0.035^2/4 = 9.621*10^-4 m^2

Therefore,

Force, F = Pressure*Area = 221325*9.621*10^-4 = 212.94 N