Question

Engineer(4) A gas gun is converted from a syringe. The outlet of the syringe is tightlysealed by a gas gun bullet. The bullet will be expelled when the pressure ofthe gasreaches 125 kPa. Initially, the syringe contains 50 cm3 of air atatmospheric pressure (100 kPa). The piston is now pushed inwards slowly.Find the volume of the air when the bullet is expelled.

Answer 1

We would apply Boyle's law which relates volume and pressure. It states that the volume of a given amount of gas held at constant temperature varies inversely with the pressure. The formula is

P1V1 = P2V2

where

P1 and P2 are initial and final pressures respectively

V1 and v2 are initial and final volumes respectively

From the information given,

V1 = 50 cm^2, P1 = 100 kPa

P2 = 125 kPa, V2 = ?

By substituting these values into the formula, we have

100 x 50 = 125 x V2

5000 = 125V2

V2 = 5000/125

V2 = 40

the volume of the air when the bullet is expelled is 40 cm^3