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Energy
What is Energy?
Energy

The ability to do work.

Work = force x distance

Energy is measured in units called
JOULES which can be abbreviated to J.
Two Types of Energy:
Kinetic and Potential

Kinetic Energy: The energy of an
object that is due to the objects motion.

Kinetic energy = mv2/2

m = mass
v2 = velocity squared
Kinetic Energy Problems



What is the kinetic energy of a car that
has a mass of 2,400 kg and is moving
at 20 m/s?
REMEMBER: mv2/2
m = 2,400 and v = 20 m/s
SO….

2, 400 x 20 x 20/2

You have to multiply by 20 twice due to
velocity being squared!!!

Answer: 4,800,000 Joules (J)
Problem #2

What is the kinetic energy of a 4,000 kg
elephant that is running at 2 m/s?

4,000 x 2 x 2/2

Answer: 8,000 J
Problem #3

What is the kinetic energy of a 2,000 kg
bus that is moving at 30 m/s?

2,000 x 30 x 30/2

Answer: 900,000 J
Final Kinetic Energy Problem

What is the kinetic energy of a 3,000
bus that is moving at 20 m/s?

3,000 x 20 x 20/2

Answer: 600,000 J
Potential Energy and
Gravitational Potential Energy

Potential Energy: energy that an object
has because of the position, shape, or
condition of the object…STORED
energy.

If the object has height the potential
energy is known as GRAVITATIONAL
POTENTIAL ENERGY.
Gravitational Potential Energy



GPE = weight x height
What is the gravitational potential
energy of a cat that weighs 40N
standing on a table that is 0.8 m above
the ground?
40 N x 0.8 m = 32 J
GPE Problem #2



What is the gravitational potential
energy of a diver who weighs 500N
standing on a platform that is 10 m off
the ground?
500 N x 10 m
5000 J
GPE Problem #3

What is the gravitational potential
energy of a diver who weighs 600 N
standing on a platform that is 8 m off the
ground?

600 N x 8 m

4800 J
Mechanical Energy

Mechanical Energy: the total energy of
motion and position of an object

mechanical energy = potential energy =
kinetic energy

Remember that mechanical energy stays the
same unless some of it is transferred to
another object.
Five Forms of Energy

Thermal

Chemical

Electromagnetic (electrical and light)

Sound

Nuclear
Thermal (Heat) Energy

Produced by random motion of particles
that make up the object

Examples: fire, friction, light bulb that
has been on, sun, stove coils
Chemical Energy

Chemical Energy: energy of a
compound that changes as its atoms
are rearranged….a substance changes
into a brand new substance.

Examples: digested food, burning
paper, rusting nail
Electromagnetic Energy

Electromagnetic energy: electrical and
light energy combined….energy of
moving charged particles.

Examples: microwave, amps, sun, light
bulbs, hair dryer, video games
Sound Energy

Sound Energy: energy that vibrating
objects transmits through the air

Examples: vocal chords, guitar strings,
musical instruments
Nuclear Energy

Nuclear Energy: comes from changes
in the nucleus of an atom; most intense
form of energy; dangerous to humans

Examples: sun, nuclear power plants,
nuclear warfare