Question

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?

Answer 1

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

Answer 2

Answer:

The force exerted by the child is 460.8 N

Explanation:

We have given that pressure $P=1.2\times 10^5pa$

Radius of the circular piston r = 0.035 m

So area $A=\pi r^2=3.14\times 0.035^2=0.003846m^2$

We have to find the force exerted by the child

We know that force is given by

$Force=pressure\times area$

So force will be $Force=1.2\times 10^5\times 0.00384=460.8N$

So the force exerted by the child is 460.8 N