Stuck on physics A2 applied topic question Watch
I was doing this paper from June 2010, and it asks you to calculate the work done by an expanding gas from a p-V diagram, but in the mark scheme it only calculates the area under the graph up to atmospheric pressure, rather than zero. Does anyone know why this is? The examiner's report said many 'failed to read the question carefully' and calculated to 0 pressure but I've read it a good few times now and can't see it!
It's question 4.a. in the link attached-thanks
The clue is in the question - "Use the graph to estimate the work done by the air as it expands from a pressure of3.6 × 10^5Pa to ATMOSPHERIC PRESSURE" not to zero as the gas never reaches zero pressure.
So the total work done is the area under the graph down to atmospheric pressure not 0 as this would imply that the external pressure was a vacuum.