In Problem 15.21, if you assume that the pressure of the gas is related to its volume by p...

In Problem 15.21, if you assume that the pressure of the gas is related to its volume by pV = constant while the gas is compressed (an isothermal process) and by pV1.4= constant while it is expanding (an isentropic process), what is the velocity of the projectile when it has returned to its original position?