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ENERGY
ENERGY

The ability to do work.

Many forms

Unit of measure: joule (J)

Amount of force of one newton over one meter.

1J =
KINETIC ENERGY


The energy of an object in motion
Kinetic energy of an object depends on its mass
and speed.
Kinetic Energy = ½mv2


If you double the mass of an object, you double
the KE
If you double the speed of an object, you
quadruple the KE
YOU SERVE A VOLLEYBALL WITH A MASS OF 2.1 KG. THE BALL
LEAVES YOUR HAND WITH A SPEED OF 30 M/S. WHAT IS THE
KINETIC ENERGY OF THE VOLLEYBALL?
KE = ½mv2
KE = ½ * 2.1kg * (30m/s)2
KE = ½ * 2.1kg * 900m2/s2
KE = ½ * 1890kg*m2/s2
KE = 945J
KE = 900J
NOW, TRY ONE FOR YOURSELF!
A 50-KILOGRAM BOY AND HIS 100-KILOGRAM FATHER WENT
JOGGING. BOTH RAN AT A RATE OF 5 M/SEC. WHO HAD MORE
KINETIC ENERGY?

KE = ½mv2
KE(boy) = ½ * 50kg * (5m/s)2
2 2
 KE(boy) = ½ * 50kg * 25m /s
2 2
 KE(boy) = ½ * 1250kg*m /s
 KE(boy) = 625J = 600J

KE(father) = ½ * 100kg * (5m/s)2
2 2
 KE(father) = ½ * 100kg * 25m /s
2 2
 KE(father) = ½ * 2500kg*m /s
 KE(father) = 1250J = 1000J

POTENTIAL ENERGY

Stored energy that is a result of position or
shape.
GRAVITATIONAL POTENTIAL ENERGY

The potential energy that is the result of an
object’s height.


The higher an object, the greater the PE
PE = mgh
m = mass
 h = height
 g = acceleration due to gravity


9.8m/s2
WHAT IS THE POTENTIAL ENERGY OF A 15.0KG CINDER BLOCK
SITTING ON A PLATFORM 10.0M HIGH?

PE = mgh

PE = 15.0kg * 9.80m/s2 * 10.0m

PE = 1470 kg * m2/s2

PE = 1470 J
GUESS WHAT’S NEXT?

That’s right….try one on your own!
WHAT IS THE POTENTIAL ENERGY OF A 80.0KG DIVER
STANDING ON A PLATFORM 10.0M ABOVE A POOL?

PE = mgh

PE = 80.0kg * 9.80m/s2 * 10.0m

PE = 7840kg * m2/s2

PE = 7840J
ELASTIC POTENTIAL ENERGY

The potential energy of an object that is stretched
or compressed.
OTHER FORMS OF ENERGY
MECHANICAL ENERGY


The energy associated with the motion and
position of everyday objects
The sum of an object’s potential and kinetic
energy.
THERMAL ENERGY


The total kinetic and potential energy contained
in the atoms of an object.
The faster the atoms in an object move, the
greater its thermal energy.
CHEMICAL ENERGY

The energy stored in the chemical bonds of a
substance.

Hydrocarbons

Exothermic reactions
ELECTRICAL ENERGY


The energy associated with electrical charges.
Work performed by the transfer of electrons from
one atom to another.
ELECTROMAGNETIC ENERGY

Energy that travels in waves.

Visible light

X-rays
NUCLEAR ENERGY

Energy stored in the nucleus of an atom

Large amounts of potential energy

Fission


The energy released when the nucleus of an atom is
split apart.
Fusion

The energy released when two small nuclei fuse
together to make one large nucleus.
ENERGY CONVERSION

Energy can be converted from one form to another

Digestion of food


Nuclear power plant


Chemical energy → mechanical energy
Nuclear energy → Electrical energy
Light bulb

Electrical energy → Electromechanical energy
WITH YOUR PARTNER, BRAINSTORM AS MANY
WAYS IN WHICH ENERGY IS CONVERTED FROM
ONE FORM TO ANOTHER AS YOU CAN THINK OF.
LAW OF CONSERVATION OF ENERGY

Energy cannot be created or destroyed.
ENERGY AND MASS

Albert Einstein

E = mc2


Where c=speed of light, 3.0x108m/s
If 1 gram of matter were converted entirely to
energy:
E = 1x10-3kg x 3.0x108 x 3.0x108 = 9x1013J