[hchawn]

The question's about a hand pump and bottle
The volume of the bottle is 3.5x10^(-4)
During the upstroke of the pump, the pump chamber volume increases from zero to 6.5x10^(-4)
Initial pressure is 99kPa
(constant temperature)

Calculate the pressure of the bottle after one upstroke


I did:
pV = 99 x 10^3 x 3.5 x 10^(-4) = 34.65

V(after upstroke) = 34.65/ (10x10^(-4)) = 34650Pa

actual answer is 83.5kPa, can anyone see how to get that?

[Fishbulb25]

(Original post by hchawn)
The question's about a hand pump and bottle
The volume of the bottle is 3.5x10^(-4)
During the upstroke of the pump, the pump chamber volume increases from zero to 6.5x10^(-4)
Initial pressure is 99kPa
(constant temperature)

Calculate the pressure of the bottle after one upstroke


I did:
pV = 99 x 10^3 x 3.5 x 10^(-4) = 34.65

V(after upstroke) = 34.65/ (10x10^(-4)) = 34650Pa

actual answer is 83.5kPa, can anyone see how to get that?

Just doing this paper now. I think the key is definitely 'On an up-stroke of the pump, air enters the pump chamber from the bottle.' So if V1 = 3.5x10^-4 then V2 (an up-stroke) is going to be that original volume plus the amount of air it's let in. So V1xP1= 3.5x10^-4 x 99000
V2xP2= (3.5x10^-4 +6.5x10^-5) x ?
then just solve for P2 and you get 83934