Law of Conservation of Energy

THE LAW OF
CONSERVATION
OF ENERGY

Energy is Everywhere

Try to think of something that doesn't
involve energy. Anything? The truth is just
about everything involves energy. Even
thinking about energy involves energy!
The chemical energy in the food you eat
transfers into electrical energy in your
brain waves, forming your thoughts.
Pretty cool, eh?

Energy Transformation Review

How is energy transformed from one form
into another?

Understanding energy transfers is a vital skill of many athletes, but also a
matter of everyday survival. When humans or animals eat, the energy from
the food is transformed within our bodies, giving us energy. Likewise, the sun
provides energy to plants, which the plant is able to transform into the sugars

it needs to fuel its own growth.
These are all examples of the
law of conservation of energy.

How is energy transformed from one form
into another?

In the 1999 X Games, professional skateboarder Tony Hawk landed a move called
"The 900." That's an aerial spin with two and a half rotations performed on a
skateboard ramp. To master the perfect "900," Hawk needed to have a large amount
of potential energy at the top of the half-pipe that could be transformed into kinetic
energy as he rolled down the ramp. Then, at just the right moment, Hawk could use
the transformed energy to successfully land "The 900."

•The Law of Conservation
of Energy is one of the
most fundamental laws
of nature.

•Energy is never created or
destroyed but it can be
converted to different forms.

•In the roller coaster system, potential energy is converted to kinetic
energy and then back to potential energy as the cars roll up the next hill,
slowing as they go.

4

Conservation of Energy

Mod I Unit 1 Lesson 2

• In every transformation

some energy is converted
to less useful forms such
as heat and sound.

• Because energy is being

converted to less useful
forms the cars can never go higher than the first hill.

• The energy has been transferred to objects or systems outside of the

system of cars

5

Conservation of Energy

Mod I Unit 1 Lesson 2

How is energy transformed from one form
into another?

It's important to note that the total energy of
the universe is constant, and energy is
conserved in a closed system. Think of a
closed system like an imaginary sealed box
where nothing goes in or out. Energy in a
closed system always remains the same
unless some of it is transformed into other
forms of energy, such as heat from friction.

Law of Conservation of Energy

What is the Law?

The Law of Conservation of Energy states that, in an isolated system, energy is not created or destroyed. Instead, energy only transfers from one place to another or transforms from one form into another.

This is just like our lesson on Chemical Equations!

Energy Transformation

• The Law of Conservation of Energy states that energy cannot be

created or destroyed, but can change from one form to another.

• ENERGY IN always equals ENERGY OUT

• Energy is conserved as it changes from one form to another.

• Energy is most noticeable when it changes forms.

Law of Conservation of Energy

What is it?

Energy is defined as the ability to do work.

​When we ride a bicycle, that is considered doing work.

When we go for a walk, that is considered doing work.

Eating throughout the day is considered doing work. ​

Any action that uses force is considered work. ​

Writing down these notes is hard work!

Law of Conservation of Energy

What is it?

There are two types for energy: Potential Energy and Kinetic Energy.

​

Potential Energy is stored energy.

​

Kinetic Energy is ​released energy.

These two branch off into many different categories!

Law of Conservation of Energy

Where does it go?

Energy does not simply disappear when released. It transfers forms ​into a new energy!

​

When we hit a baseball with a bat, we transfer mechanical energy from the bat onto the ball, making it fly over the fence!

​

Energy is not created or destroyed, it changes forms!

Law of Conservation of Energy

Where does it go?

Energy not only transfers to another object, but it can also transform!

​The Sun emits radiant energy, that transforms to thermal energy when it touches the Earth's surface!

​When the Sun's radiant energy reaches plants on Earth, it transforms into chemical energy using photosynthesis!

​

Conservation of Energy in Action

At the top of the ramp,
the skater has the highest
potential energy (100 J)
because he is at the
highest point above the
ground. He has no kinetic
energy (0 J), because he
has no speed or motion.
The total energy in this
system is 100 joules (J).

Conservation of Energy in Action

As the skater first begins
to move down the ramp
and closer to the ground,
he starts to lose potential
energy (80 J) but gains
kinetic energy (20 J) as the
potential energy
transforms into kinetic
energy. The total energy
of the system is still 100 J.

Conservation of Energy in Action

As he continues farther
down the ramp, the
potential energy will
continue to decrease (60
J) as it transforms to
kinetic energy (40 J) of
speed and motion.

Conservation of Energy in Action

As the skater continues
down the ramp gaining
kinetic energy (60 J) as
speed, the potential
energy (40 J) will continue
to decrease as the energy
transforms.

Conservation of Energy in Action

As the skater nears the
very bottom of the ramp,
the potential energy
decreases (20 J) as he
moves closer to the
ground and the kinetic
energy increases (80 J) as
his speed continues to
increase.

Conservation of Energy in Action

Once the skater reaches the bottom of
the ramp, he is closest to the ground
with the lowest potential energy (0 J)
and the highest amount of kinetic
energy (100 J). The law of conservation
of energy can be observed as we trace
the path of the skater on the ramp. By
adding the potential energy to the
kinetic energy, we can calculate that the
total energy was always equal to 100 J.,
proving that no energy was created or
destroyed.

Summary

The law of conservation of energy states that
energy cannot be created or destroyed.
Energy can be transferred between objects or
be transformed from one form of energy into
another. Because of this, the total amount of
energy in a closed system never increases or
decreases, it remains the same. Energy
transformations are happening all around us.
Every time we move, cook, listen to music, or
even simply turn on a computer, you can be
sure that energy transformations make it
happen.

Multiple Choice

According to the ____________________, energy cannot be created or destroyed.

• kinetic

• law of conservation of energy

• energy transformation

• potential

Multiple Choice

A change from electrical to radiant energy to thermal energy is called a(n) ____________.

• electrical

• radiant

• energy transformation

• law of conservation of energy

Multiple Choice

Suppose you are shooting a basketball toward a hoop. As the ball rises in the air, its __________ energy increases and its __________ energy decreases.

• potential, kinetic

• kinetic, potential

• friction, kinetic

• potential, friction

Multiple Choice

As the ball falls back toward the floor, its _________ energy increases and its ___________ energy decreases.

• thermal, potential

• kinetic, potential

• potential, kinetic

• kinetic, friction

Multiple Choice

You use a lamp to change _________ energy into _________ energy.

• electrical, radiant

• potential, radiant

• potential, thermal

• electrical, potential

Multiple Choice

At which point would this roller coaster possess the most kinetic energy?

• 1

• 2

• 3

• 4

Multiple Choice

At which point would this roller coaster possess the greatest amount of potential energy?

• 1

• 2

• 3

• 4

Multiple Choice

Stored energy due to position is called __________.

• Kinetic Energy

• Potential Energy

• Mechanical Energy

• Electric Energy

Multiple Choice

________ is the energy possessed by an object because of its motion.

• mechanical energy

• gravitational energy

• potential energy

• kinetic energy

Multiple Choice

Energy can be created.

• True
• False

Multiple Choice

Energy cannot be destroyed.

• True 
• False

Multiple Choice

When something is dropped, what type of energy transfer takes place?

• Kinetic -> Potential
• Gravitational Potential -> Kinetic -> Sound
• Electrical -> Chemical
• Heat -> Nuclear

Multiple Choice

According to the Law of Conservation of energy, the amount of energy before and after a reaction must be the same. Which statement below is true?

• The total amount of energy is conserved
• The total amount of energy is less after a reaction
• The total amount of energy is more after a reaction

Multiple Choice

The Law of Conservation of Energy states:

• Energy can created or destroyed but not transformed 
• Energy cannot be created or destroyed, it can only transformed
• Energy can't be created, destroyed or transformed

Multiple Choice

Potential or kinetic?
Running?

• potential
• kinetic

Multiple Choice

A change from electrical to radiant energy to thermal energy is called a(n) ____________.

• electrical

• radiant

• energy transformation

• law of conservation of energy