In Fig. 17, the accelerating forces acting on the mass M are shown. The acceleration
considered is a single pulse of magnitude Ag, lasting for a time interval t,. It would be possible
to consider a sinusoidal pulse, but this complicates the expressions unnecessarily. The
resisting acceleration, Ng, is shown by the dashed line in Fig. 17. The accelerating force
lasts only for the short time interval indicated, but the decelerating force lasts until the direction
of motion changes.