# What are some examples of the principle of conservation of energy?

Oct 5, 2015

Examples include a pendulum, a ball tossed up in the air, a skier sliding down a hill and the generation of electricity inside a nuclear power plant.

#### Explanation:

The principle of the conservation of energy says that energy within an isolated system is neither created nor destroyed, it simply changes from one type of energy to another.

The most difficult part in conservation of energy problems is identifying your system .

In all of these examples, we will ignore the small amount of energy lost to fiction between the object and air molecules (air resistance or drag)

Examples:

• A pendulum:
As the pendulum swings down:
gravitational potential energy of the pendulum $\to$ kinetic energy of the pendulum
As the pendulum swings up:
kinetic energy of the pendulum $\to$ gravitational potential energy of the pendulum

• A ball tossed up in the air:
During the throw:
Chemical energy from your muscles $\to$ kinetic energy of the ball
As the ball reaches its peak:
kinetic energy of the ball $\to$ gravitational potential energy of the ball
As the ball falls down:
gravitational potential energy of the ball $\to$ kinetic energy of the ball

• A skier slides down a hill:
gravitational potential energy of the skier $\to$
kinetic energy of the skier + thermal energy of the snow and skies (from friction)

• A compressed spring launches a ball in a pinball game:
Elastic potential energy of the spring $\to$
kinetic energy of the ball

• Inside of a nuclear power plant:
nuclear energy (from the decay of uranium) $\to$
thermal energy of water $\to$
kinetic energy of a turbine $\to$
electrical energy + thermal energy (from friction in the turbine and transmission lines)