The standing vertical jump is a good test of an athlete's
strength and fitness. The athlete goes into a deep crouch, then
extends his legs rapidly; when his legs are fully extended, he
leaves the ground and rises to his highest height. It is the force
of the ground on the athlete during the extension phase that
accelerates the athlete to the final speed with which he leaves the
ground. A good jumper can exert a force on the ground equal to
twice his weight. If his crouch is 55 cm deep,
how far off the ground does he rise?
