Slide 1

Energy


Slide 2

What is Energy?
• Energy is the ability to cause change

• Any time you move, or move something you are
using energy


Slide 3

Forms of Energy
• What are some forms of energy?

• Electrical – energy in the form of moving
electrons
• Chemical – energy from a chemical reaction
• Thermal – energy of heat
• Radiant – the energy of electromagnetic waves
including light, gamma rays, microwaves


Slide 4

Converting Energy
• Energy can be converted between it’s different
forms
• Radiant Energy is converted to chemical energy
through photosynthesis


Slide 5

• Chemical energy
is turned into
thermal energy in
a fire.


Slide 6

• Thermal
energy is
turned into
electrical in a
power plant.


Slide 7

• Electrical energy is
turned into radiant
energy in a lightbulb.


Slide 8

Kinetic Energy
• Kinetic energy is the energy of movement

• KE = ½ mv2
• m is the mass of an object, v is the velocity of an
object
• Standard units – kg m2/s2 or Joules (J)


Slide 9

Example
• A jogger who’s mass is 60 kg is moving at 3 m/s,
what is the jogger’s kinetic energy?
• m = 60 kg, v = 3 m/s
• KE = 1/2(60kg)(3 m/s)2 = 270 J


Slide 10

Example
• A car moving at a speed of 20 m/s has a KE of
300,000 J. What is the car’s mass?


Slide 11

Example
• A sprinter has a mass of 62.5 kg and a KE of
4000 J. What is the sprinter’s velocity?


Slide 12

Potential Energy
• Potential energy is stored energy

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5 Types of Potential Energy
Elastic
Chemical
Electrical
Nuclear
Gravitational


Slide 13

Elastic
• Elastic Potential Energy
is energy stored by
something that can
stretch or compress


Slide 14

Chemical
• Chemical Potential Energy is the energy stored
in the chemical bonds between atoms.


Slide 15

Electrical
• Electrical Potential Energy is the energy due to
the position of an electric charge


Slide 16

Nuclear
• Nuclear Potential Energy
is the energy stored in the
nucleus of an atom
• If you could release all of
the nuclear potential
energy in you body, you
could power the United
States for 6 years.


Slide 17

Gravitational
• Gravitational Potential
Energy is energy
stored due to an
object’s position above
the Earth’s surface


Slide 18

Formula for Gravitational Potential
Energy
• PE = mgh
• m is the mass of an object, g is the acceleration
due to gravity, h is the height above the Earth
• Standard units – kg m2/s2 or Joules (J)


Slide 19

Example
• A 65 kg rock climber climbs a cliff. What is the
climber’s potential energy when she is 35 m
above the base of the cliff?
• m=65 kg, h=35m, g=9.8 m/s2
• PE = mgh = (65kg)( 9.8 m/s2)(35m) = 22295 J


Slide 20

Example
• What is the mass of a hiker 200 m above the
ground if her GPE is 117600 J?


Slide 21

Example
• Find the height of a baseball with a mass of .15kg
and has a GPE of 73.5 J?


Slide 22

Kinetic or Potential
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a moving skateboard,
a rock at the edge of a cliff,
an unconnected battery,
a baseball being pitched,
a gallon of gas,
a stretched rubber band,
a moving car,
a person climbing stairs
a pizza


Slide 23

Energy can change forms
• What happens when you turn on a lightbulb?
• What happens to the lightbulb if you leave it on
for a long time?


Slide 24

Conversions
• Mechanical energy is the total amount of kinetic
and potential energy in a system.
• ME = KE + PE


Slide 25

Law of Conservation of Energy
• Law of Conservation of Energy – energy can not
be created or destroyed, only transformed.