A block of mass is placed on top of a movable piston with mass and area in a cylindrical container filled
with an ideal gas. The block and piston are pushed down until the gas is at pressure . When the block and piston
are released, they accelerate upward. Free-body diagrams for the block and piston are shown. is the force
exerted on the block by the piston, is the force exerted on the piston by the gas, and is the force exerted
on the piston by the block. Which of the following gives a correct equation for as the piston accelerates
upward?