Download Law of Conservation of Energy

The Law of Conservation of Energy
Section 5.3 Part 2
Energy comes in many different forms. Interactions between these types of
energy are governed by the Law of Conservation of Energy:
Law of Conservation of Energy
Energy cannot be created or destroyed. It can be changed from one form
to another, but the total amount of energy in the universe stays constant.
For example, when diver jumps from a springboard:

Chemical energy from the muscles is converted into elastic energy in the
springboard.

When the board releases, the elastic energy is converted into the kinetic
energy (upward speed) of the diver.

As the diver moves towards the maximum height, kinetic energy is
converted in to gravitational potential energy.

On the way back down, the gravitational potential energy is converted
back into kinetic energy.

When the diver hits the water, the kinetic energy is converted in sound
energy, thermal energy, kinetic energy of the water, and work done in
water displacement.
Even after the diver enters the water, the energy has not disappeared. It is
eventually mostly converted into thermal energy which remains in the room, or
dissipates out into the environment.
Although the above example illustrates several complicated energy
transformations, generally it’s only the transformation between gravitational and
kinetic energy that will be studied in this section.
Whenever an object is in free fall, it is undergoing energy transformations. The
total amount of energy in the system is constant (according to the law of
conservation of energy), but the relative amounts of gravitational and kinetic
energy change.
At its maximum height, an object would have entirely gravitational potential
energy. As it starts to fall, its height DECREASES and it is gravitational potential
energy DECREASES. This energy does not disappear but is converted into the
kinetic energy. As the object falls, its velocity INCREASES causing its kinetic
energy to INCREASE. The change in gravitational energy equals the change in
kinetic energy. A useful expression to summaries this interaction is:
Etotal = Ek + Eg