Energy: It is the ability to do work. The main type of energy is mechanical energy.
Mechanical Energy: The energy due to the position and movement of an object.
Potential Energy: Stored energy. It depends on the weight and the height of the object.
Kinetic Energy: Energy of motion. It depends on the mass and the speed of an object.
Chemical Energy: It is energy stored in the bonds of chemical compounds. The chemical energy can be found in food, and this energy can be converted into mechanical energy and heat by the body.
Gravitational Energy: Gravitational energy is the potential energy a body with mass has in relation to another massive object due to gravity. It is the potential energy associated with the gravitational field.
Elastic Energy: It refers to the energy that is stored when a force is applied to deform an elastic object, and it is stored until the force is removed and the object returns to its original shape.
Applying the terms in jumps:
During a grand jete (Figure 4), the dancer experiences different types of energy such as chemical, kinetic, potential, gravitational, and elastic energy.
- The first type of energy that is present is chemical energy, which is present all the time, when the dancer jumps, as well as when she is still. The chemical energy in the food the dancer ate is present before the jump, and it is converted into mechanical energy that is used to perform the jump, as well as heat that is emitted from the dancer's body.
- The next types of energy are kinetic and potential energy. When the jump starts she has a lot of kinetic energy and is gaining potential energy. At the highest point of the jump that energy transforms into less kinetic energy and more potential energy. Finally, as she lands the energy is completely kinetic energy, until she stops. When she lands the energy is transferred to the floor as well.
- The third one is gravitational energy, which again is present all the time in the dancer's body. When the dancer is standing on the floor, she experiences the pull that the center of the Earth is exerting on her body, which is her normal gravitational energy, but as she performs the jump, and moves higher, further apart from the center of the Earth, the gravitational energy in her body is increasing, which is what pulls her back down.
- The last type of energy is elastic energy. When applying a force to deform, stretch or bend an object you are storing elastic energy that is stored in the object, in this case in the dancer, until it goes back to its original shape. The dancer has elastic energy at the beginning of the jump as she bends her legs to get the impulse she needs to perform the jump. Then, as she jumps she gains elastic energy when she extends her legs (they are stretching), and opens them in the position of the jump. Finally, as she lands she retracts her legs to the original position they had, and that's when she releases all of the stored elastic energy she accumulated.
- As the kinetic, potential, gravitational and elastic energy are all types of mechanical energy the dancer experiences mechanical energy throughout the whole jump.
Figure 4
