With several feet of car body in front of the driver, the energy of a crash can be dissipated and the suddenness of the change in velocity can be reduced, they say.

He used a body swerve to shake off a marker and create space for himself. Then, with marvelous disguise, with the merest of back lift from his left foot, he propelled the ball at startling velocity.

The velocity increasing, the acceleration of a body is positive.