The force required to compress the gas in a gas spring a distance x is given by

Question:

The force required to compress the gas in a gas spring a distance x is given by
F = constant/xk
where the constant is determined by the geometry of this device and k is determined by the gas used in the device. One such device has a constant of 200 lbf·in1.4 and k 5 1.4. Determine the work, in Btu, required to compress this device from 2 in to 7 in.