IF the volume of gas is plotted against the reciprocal of pressure, the slope will be given as Slope = V/1/P = P x V thus the unit of the slope will be; P = ForceArea = Nm-2, = V = M3 = NM. The unit NM (Newton - Meter) is the practical unit of work, which is the product of force (N) and Displacement (M). Note: It should be noted that the practical unit of work is Newton-Meter, whereas its S.I unit is Joules, just as energy.