Forms of Energy

Forms of Energy

What is energy?

Vocabulary

Energy: the ability to cause motion or change

Kinetic energy: the energy an object has due to its motion

Potential energy: the energy stored in a system due to the positions of objects in
the system that are interacting at a distance

Law of conservation of energy: a scientific law that states that the total energy of
an isolated system always remains the same

1. Energy

Energy: the ability to cause motion or change

Everything around you has energy

-Explains complex interactions

Hammer, nail and wood example: moving hammer has energy, energy is transferred
to the nail, which is then transferred to wood.

When an object exerts a force on a second object, and the second object moves in
the direction of the force, the force adds energy to the second object.

If an object exerts force on a second object, the second object moves in the
opposite direction as the force acts, the force subtracts energy.

Open Ended

Why do scientists track energy in a system?

2. The Two Forms of Energy

Potential energy: the energy stored in a system due to the positions of objects in
the system that are interacting at a distance

-Exists when objects within the system are interacting in a force field

-The positions of the objects determine how much potential energy there is

Snowboarder example: at the top of a mountain, the snowboarder has the most
potential energy but once they reach the bottom of the hill they can’t go anywhere
else.

Kinetic energy: the energy an object has due to its motion

All moving objects and particles have kinetic energy because they have the ability
to move another object or particle and cause it to move or change.

Snowboarder example: the snowboarder moving at all has kinetic energy

2. The Two Forms of Energy

Both Forms of Energy:

The system with the snowboarder gliding down the mountain has both kinetic and
potential energy because they are moving and and can potentially keep moving
until they get to the bottom of the mountain.

Open Ended

A system with a snowboarder going down a hill has what kind of energy? Kinetic? Potential? Or both?

3. Tracing Energy Transformation in a System

A snowboarder experiences different amounts of potential energy and different
amounts of kinetic energy at different points along the hill.

4. Conservation of Energy

Law of conservation of energy: a scientific law that states that the total energy of an
isolated system always remains the same

●Energy cannot be created or destroyed

○Energy can be converted though, so the given energy might not always stay the same

Isolated system: a system that does not have any energy inputs or outputs

●An object’s energy can be transferred to another object in the isolated system when
the two objects exert forces on each other

Kinetic energy of the rolling cue ball can be transferred to a pool ball when they collide, so
that pool ball now has kinetic energy.

●The total amount of energy in a game of pool remains the same and is equal to the
starting energy of the cue ball

4. Conservation of Energy

But pool balls stop rolling eventually, which means they no longer have kinetic
energy…

Energy is conserved, but some energy can be lost

●The sound the balls make when they hit each other

●Friction

Energy of the cue ball is converted into kinetic energy (vibrating sound particles or
heat), energy is still conserved.

the sum of the particles’ energy plus all the other energy in a system will always
be the same

Open Ended

What is the law of conservation of energy in your own words?