The pole vault is an Olympic event that demands a very high level of athletic ability. Nevertheless, it illustrates very simply the law of conservation of energy. The vaulter tries to achieve maximum kinetic energy by sprinting down the runway. At the end of the approach, the flexible fiberglass pole is planted in the box at the base of the pit. The kinetic energy gained in the sprint is converted into potential energy stored by elastic deformation of the pole. This, in turn, is converted into gravitational potential energy as the vaulter attempts to clear the crossbar.
For a person with a height of
meters, the body's center of gravity is estimated to be at 0.55
. Suppose the athlete can achieve a maximum speed of
meters/second (world-class sprinters can do 10 m/sec). For the center of gravity to successfully reach the height
of the crossbar, the energy relation
must be satisfied, where
is the acceleration of gravity, 9.81 m/sec
. This result assumes perfect technique as well as 100% efficient conversion of energy at each stage. The effects of wind resistance, crowd noise, and other distractions are neglected. Likewise neglected is the possibility of additional lift achieved by pushing down on the pole just before release.
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