Top: rate at which kinetic energy is swept into the SNR shell (red curve, labeled “1”), rate at which kinetic energy is lost due to deceleration of the shell (blue curve, labeled “2”), and the net rate of change of kinetic energy in the SNR shell (green curve, labeled “3”). Bottom: integrated kinetic energy corresponding to the three terms shown in the upper panel. Curve 3 gives the accumulated swept-up kinetic energy, E_su(t).