The first law of thermodynamics, also known as the principle of conservation of energy, states that energy cannot be created or destroyed, only transferred. The energy transfers that take place during the pole vaulting process demonstrate this principle many times over, with five different energy transfers taking place during the course of a single vault.
Chemical to Kinetic
The athlete begins the pole vault from a standing start and all his energy is stored in his body. This storage takes the form of chemical energy reserves, which are consumed during respiration to provide the kinetic energy that moves the athlete's muscles. This, in turn, propels the athlete forward.
Kinetic to Potential
As the pole vaulter lifts into the air, his speed reduces in line with a reduction in his kinetic energy. The kinetic energy is reduced in line with Newton's laws of motion, becoming gravitational potential energy. This is energy stored in the athlete as a result of his distance from the ground, rather than energy stored in his cells. When all the kinetic energy is converted to potential energy, the athlete stops rising.
- As the pole vaulter lifts into the air, his speed reduces in line with a reduction in his kinetic energy.
Potential to Kinetic
The athlete begins to fall back to the ground once all of his upward motion has ceased. As he falls, he begins to build up speed once more and will be travelling at approximately the same speed when he reaches the ground as he was travelling when he first lifted into the air. This is because his gravitational potential energy is converted back into kinetic energy during the fall.
Kinetic to Heat and Sound
Because energy cannot be created or destroyed, the kinetic energy must go somewhere when the athlete hits the ground. In the case of our pole vaulter, a lot of the kinetic energy becomes heat energy due to friction and other forces occurring on contact with the landing mat. The kinetic energy that does not become heat instead becomes sound energy, which is how we can hear the athlete land.
Chemical, Kinetic and Potential Energy to Heat
The energy transfer process is not 100 per cent efficient. At each stage in the pole vault, energy is lost as heat. In the chemical to kinetic transfer, heat is produced due to inefficiencies in the respiration process (which is also why you get hot when you exercise), while in the conversions between kinetic and potential energy, wind resistance causes minor amounts of friction that sap the athlete's energy.