Energy Transformations

1. ENERGY & POWER
Part 1
The Nature of Energy
Brought to you by MixMaster Speer© & The Good People at Krispy Kreme®.

2. What is Energy?
• The ability to do work or cause change is
called energy.
• OK…but what’s work?
• Work is done when a force moves an
object through a distance.

3. OK…But what’s a FORCE?
• A FORCE IS A PUSH OR PULL
• FORCES ARE MEASURED IN
NEWTONS

4. TYPES OF ENERGY
• The two types of energy are KINETIC &
POTENTIAL.
• What type you have depends on whether
an object is moving or not.

5. KINETIC ENERGY
• The energy of
motion is called
kinetic energy.
I can’t
swim!

6. What Affects Kinetic Energy?
• K.E. depends on an objects mass and its
velocity.
THINK: Which ball
would you have to push
harder to get rolling?
Once rolling the
bowling ball would
have more kinetic
energy than a golf
ball rolling at the
same velocity.

7. CALCULATING KINETIC ENERGY
• KINETIC ENERGY = MASS x VELOCITY2
2
Sometimes written (1/2)mv2
NOTICE: Changing the velocity of an object
will have a greater effect on its kinetic
energy than changing its mass. Why?

8. WHAT ARE THE UNITS?
• KINETIC ENERGY = MASS x VELOCITY2
2
K.E. = kg x m2
s2
instead of saying all that we use the Joule!

9. SAMPLE PROBLEM
• FIND THE K.E.
A 10 kg wagon moving at 5 m/s
• KINETIC ENERGY = MASS x VELOCITY2
2
10 x (5)2
divided by 2
10 x 25 divided by 2
250 divided by 2
125… what were those units? kg.m2
/s2
or JOULES

10. POTENTIAL ENERGY
• Potential Energy is energy that is stored
and ready to use.

11. Hmmm…Do
I have kinetic
or potential
energy?
I KNOW!
I KNOW!
Weeee!

12. TYPES OF POTENTIAL ENERGY
• ELASTIC –the energy of an object that is
stretched or compressed

13. GRAVITATIONAL POTENTIAL
ENERGY
• Potential Energy That Depends on Height
• G.P.E. = Weight (measured in Newtons) x
Height (measured in meters)
So..the units are NxM?
YUP!
Guess what? A NewtonMeter equals…
A JOULE!!!

14. Uh…Wait a second.
• What if I don’t know an objects weight in
Newtons?
• EASY: just multiply it’s mass (in Kg)
times the acceleration caused by gravity
(9.8m/s2
)
Example: An object with a mass of 10kg
would weigh how many newtons?
RIGHT! 98 Newtons!

16. G.P.E. Sample Problem
• A hiker weighing 680 Newtons climbs up a
hill 40 meters high. How many Joules of
G.P.E. has the hiker gained?
G.P.E. = Weight x Height
680N x 40m= 27,200 Nm
-OR- 27,200 Joules!

18. DIFFERENT FORMS OF ENERGY
• MECHANICAL
• THERMAL
• CHEMICAL
• ELECTRICAL
• ELECTROMAGNETIC
• NUCLEAR
Why won’t
Bieber call
me
back???

19. MECHANICAL
• The energy
associated with
motion or
position of an
object.
Yeah I’m
the next
Tony
Hawk!
Uh…I
don’t
think so
dude!

20. THERMAL
• The TOTAL energy of the particles in an
object (kinetic + potential).

21. CHEMICAL
• The potential energy stored in chemical
bonds that hold compounds together.

22. ELECTRICAL
• The energy of moving electric charges.

23. ELECTROMAGNETIC
• Energy That Travels in Waves.

24. NUCLEAR
• A type of potential
energy
• Stored in the nucleus
of the atom
• Released during
nuclear reactions

25. Part 1 Check for Understanding
1. Are energy and work the same thing? Explain
2. How are kinetic and potential energy differen
3. List the forms of energy and give an example
4. A boulder the weighs 200N is sitting at the ed

26. • Work and energy are not the same thing,
even though they are measured in the
same units. Energy is the ability to do
work. As work is done, energy is
transferred from one object to another.

27. • Kinetic energy is the energy of motion.
Potential energy is stored energy; it has
the potential to do work.
Hey Nicki, DON’T
Call Me
CLIFFORD!

28. • Mechanical – riding a bike
• Thermal – hot water
• Chemical – food
• Electrical – batteries
• Electromagnetic – TV Remote
• Nuclear – fusion in a star

29. • GPE = Weight x Height
• GPE = 200 N x 100 m = 20,000 J

30. ENERGY & POWER
Part 2
Energy Conversion &
Conservation

31. ENERGY CONVERSION
• Most forms of energy can be converted
into any other form.
Examples: A toaster converts electrical
energy into thermal energy.
Your body converts chemical energy into
mechanical.

32. MULTIPLE CONVERSIONS
• Often a series of conversion is needed to
do a task.
• Consider lighting a match:
– Chemical to mechanical to thermal to
electromagnetic.

33. CONVERSION IN A WATERFALL
The water at the top of
the falls has G.P.E.
because it is higher than
the bottom falls.
THINK:
As the water falls
describe how G.P.E.
and K.E. change.

34. CONVERISION IN JUGGLING
Any object that falls experiences a
change in its kinetic and
gravitational energy.
Watch the ball: As it rises it slows
down. Its K.E. decreases.
BUT…because its height
increased its G.P.E. has
increased.

35. CONVERSION IN A POLE VAULT
The vaulter runs to gain K.E.
When he plants the pole it
begins to bend.
THINK: What type of energy
is he giving the pole?
RIGHT! Elastic.
Slowly the elastic is changed
to G.P.E.
Once over the bar the G.P.E.
is changed to K.E.

36. CONVERSION IN A PENDULUM
The pendulum is a continuous
conversion between K.E. and
G.P.E.
THINK: Where does the
pendulum have the greatest
G.P.E.?
Where does it have the greatest
K.E.?
Why doesn’t it swing forever?

37. CONSERVATION OF ENERGY
So…the pendulum doesn’t swing forever.
BUT, does that mean the G.P.E. we gave the
pedulum was lost or destroyed?
NO! The Law of Conservation of Energy states that
when one form of energy is converted to another,
no energy is lost or destroyed in the process.
According to The Law of Conservation of Energy,
energy can not be created or destroyed.
So…where did the energy in the pendulum go?

38. ENERGY & FRICTION
• As the pendulum moves friction slow it
down.
• When an object experiences friction the
motion of its atoms increases.
• This means its THERMAL ENERGY
increases.
• So the G.P.E changed to K.E.
and finally to heat.

39. ENERGY & MATTER
• Einstein theory of relativity added a small change to the
Law of Conservation of Energy.
• Energy can sometimes be created…
BY DESTROYING MATTER!
• We use this technique in nuclear power plants to
produce huge amounts of energy from tiny amount of
matter.
• REMEMBER: Energy and matter may sometimes
change forms BUT neither is ever created or destroyed!

40. CONSERVING ENERGY
• Conserving energy isn’t the same as the
Law of Conservation of Energy.
• Conserving energy means we should not
waste our non-renewable energy sources
like coal and gasoline.

41. Part 2 Check for Understanding
1. What is energy conversion?
2. State the law of conversion of energy in your
own words.
3. Describe the energy conversion that occurs
when a ball is dropped and bounces back up.
Why does it bounce a little lower each time?
4. A roller coaster car with a mass of 500kg is at
the top of a hill that is 30 m high. Without
friction what would it KE be as it reached the
bottom of the hill?

42. ENERGY CONVERSION

43. LAW OF CONSERVATION OF
ENERGY

44. BOUNCING BALL
• As it falls it gains K.E. and loses G.P.E.
• When it hits K.E. is converted to elastic
potential
• As it bounces back up elastic potential is
converted to K.E.
• As it rises K.E. decreses and G.P.E.
increases
• Some energy is lost to sound and heat
each time the ball bounces so eventually it
stops.

45. • Well, K.E. = (1/2)mv2
• OH #$*%! we don’t know don’t know the
velocity 
• BUT…we know that G.P.E. at the top has to
equal K.E. at the bottom!
• G.P.E. = mass x height
• OH #$*%!...the mass isn’t in NEWTONS!
But we can convert by multiplying by 9.8!
So, (9.8 x 500) x 30 = 147,000 JOULES!

46. ENERGY & POWER
Part 3
Energy Conversions & Fossil
Fuels

47. Part 3 Check for Understanding
1. How is the chemical energy in fossil fuels
related to the sun’s energy?
2. How is the energy of coal released?
3. Describe the energy conversions
involved in the formation of coal.
4. What general statement can you make
about the supply of fossil fuels? (Hint:
think about how they form).

48. ENERGY & POWER
Part 4
Power

49. Part 4 Check for understanding
1. State the formula for calculating power.
2. How are power and energy related?
3. Find the work you do when you exert a
force of 40N to run a distance of 18m in
4 seconds. Now find the power you
used.
4. The motor of an electric fan converts
24,000 J of electric energy every 60 sec.
What is the power of the fan’s motor?

50. ENERGY
WORKJOULESKINETIC
ENERGY
POTENTIAL
ENERGY
ELASTIC GRAVITATIONAL POWER