1. The problem statement, all variables and given/known data A wheel has volume 1.2 x 10-3 m3 when being full. A pump has working volume of 9 x 10-5 m3. How many times do you need to push the pump to fill the air to the wheel (initially there is no air in the wheel) until the pressure is 3.0 x 105 Pa? The atmospheric pressure is 1.0 x 105 Pa and there is no change in temperature 2. Relevant equations PV/T = constant 3. The attempt at a solution I think my attempt is really really weird, but I'll post it anyway.... P1.V1 = P2.V2 1.0 x 105.V1 = 3.0 x 105 . 1.2 x 10-3 V1 = 3.6 x 10-3 ΔV = V1 - V2 = 2.4 x 10-3 Number of pumping = 2.4 x 10-3 / 9 x 10-5 = 80 / 3 ≈ 27 times Actually, my idea is to find the initial volume of air in the wheel. The difference between the initial and final volume is the volume needed to be pumped to the wheel. But I think the final volume should be greater (my calculation shows the opposite). At the beginning, I take the pressure of the wheel the same as atmospheric pressure. Another thing that bothers me is the sentence "initially there is no air in the wheel". It means the initial volume is zero ????