yahoo answer: As soon as the pole vaulter passes over the bar, they are almost stationary, having reached the maximum height reached above ground, so apart from a little amount of kinetic energy as a result of passing over the bar, all the energy put into the vault is bound up in gravitational potential energy. During the approach, the jumper runs up so has acquired kinetic energy. Then during the vault they exert force on the pole to gain height, and to convert the horizontal kinetic energy into a vertical direction. This force comes from the chemistry of the muscles of the body. So the overall conversion is from kinetic energy plus muscular chemical energy into gravitational potential energy, which is then converted back to kinetic energy on the descent.
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