Acylinder of gas is compressed by a piston from an initial volume of 125 liters to a final volume of 90 liters. the compression occurs at constant pressure, and the work done on the gas by the piston is 104 joules. what is the gas pressure during the compression? (1 liter = 10-3 meters3)

Since the process occurs at constant pressure, the work done by the gas on the piston is given by

where
W is the work
p is the pressure
is the final volume
is the initial volume

In our problem, we have


(where the negative sign means the work is done by the piston on the gas)

We can re-arrange the previous equation and use these values to find the pressure: