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D.S.Q.
• 1. What is kinetic energy?
• 2. What are some examples of kinetic energy?
Activity
• 1. Create a line of dominoes by standing each
domino on its tall end. Space them close
enough together so they will hit each other
when they fall.
• 2. Your line may be straight or curved.
• 3. When the line is built, knock over the first
domino with your finger and observe what
happens.
Discussion
• 1. What did you observe when you knocked
over the first domino in the chain?
• 2. How is this an example of kinetic energy?
• 3. How could you modify this experiment to
stop the chain of falling dominoes before it
reaches the end?
• 4. How could you modify the experiment to
increase the kinetic energy in the middle of
the chain?
Energy
Energy & Work
• Work is done when a force moves an object.
• For example: Putting a book into your
backpack
• Energy is the ability to do work or cause
change
• When energy is transferred, the object upon
which the work is done gains energy
• Energy & work is measured in Joules
Power & Energy
• Power is the rate at which work is done
• Power = Energy Transferred
•
Time
What are 2 types of energy?
• Potential and Kinetic Energy
• Kinetic Energy is energy in motion
• Potential Energy is stored energy
Kinetic Energy
• Kinetic energy of an object depends on both
its speed and its mass
• What if you were hit with a tennis ball that
was lightly tossed at you? Would it hurt?
• Now, what if you were hit with the same
tennis ball but at a greater speed?
• The faster an object moves, the more kinetic
energy it has
Kinetic Energy Continued
• Kinetic energy also increases as mass
increases
• Which would have more kinetic energy, a
tennis ball or a bowling ball?
Calculating Kinetic Energy
• Kinetic energy= Mass x Speed²
•
2
• Example: Suppose a boy is pulling a 10 kg
wagon at a speed of 1 m/s. What is the
kinetic energy?
• 10 kg x 1 m/s²
•
2
• Answer: 5 Joules
Do the Math!
• Mrs. Kurtishi and her turtle are running. The
turtle has a mass of 20 kg. Mrs. Kurtishi has a
mass of 60 kg.
• 1. Suppose both the turtle and Mrs. Kurtishi
run at a speed of 2 m/s. Calculate both of
their kinetic energies.
• K.E of the turtle=
• K.E. of Mrs. Kurtishi =
EXTRA PRACTICE TIME!
Potential Energy
• An object does NOT have to be moving to
have energy
• Example: When you compress a spring by
winding a toy, you transfer energy to it.
However, the energy that is stored in it, might
be used when it unwinds.
• Again, P.E. is stored energy, that results from
the position or shape of an object
Solving for Potential Energy
• Formula is…
•
•
•
•
•
•
P.E. (Joules) = Mass (kg) x Gravity (9.8 m/s²) x Height (m)
OR you can solve P.E. by using the formula….
Weight (N) x Height (M)
MAKE SURE TO CONVERT MASS INTO WEIGHT.
INORDER TO DO THAT, WEIGHT = MASS X GRAVITY
Now lets practice:
• A 3.0 kg scrub jay is squawking in an oak tree in Mrs.
Fifield’s backyard. If the bird is on a branch located 20.0
m from the ground, how much potential energy does it
have?
Gravitational Potential Energy (GPE)
• Potential Energy related to an object’s height
is known as gravitational potential energy
• GPE is equal to the work done to lift to that
height
• GPE (Joules) = Weight (N) x Height (Meters)
• Example: If a book weight 10 N and if the book
is lifted 2 meters off the ground, what is the
GPE?
Elastic Potential Energy (E.P.E)
• An object has a different type of potential
energy due to its shape.
• E.P.E. is the energy associated with objects
that can be compressed or stretched.
• Ex. Trampoline
EXTRA PRACTICE TIME
Forms of Energy
• Mechanical energy is the form of energy
associated with the motion, position or
shape of an object.
• Example: a falling basketball, moving car and
trophy on a shelf
Calculating Mechanical Energy
• M.E. is a combination of both kinetic and
potential energy
• The basketball in the next image has both p.e.
and k.e. The higher the ball moves, the greater
its p.e and the faster the ball moves, the
greater the k.e.
• Mechanical Energy = P.E. + K.E.
Now you try!
P.E. = 20 J
K.E. = 2 J
M.E. =
P.E. = 12 J
K.E. = 10 J
M.E. =
Mechanical Energy & Work
• An object with mechanical energy can do
work with anther object.
• For example:
• A basketball does work on the net as it falls
through the hoop. The net moves as a result.
• The more mechanical energy an object has,
the more work it can do.
What are other forms of energy?
• Forms of energy associated with the particles
of objects include nuclear energy, thermal
energy, electrical energy, electromagnetic
energy and chemical energy
Nuclear Energy
• Atoms are the small particles that make up
objects
• The center of an atom is called the nucleus
• A type of potential energy called nuclear
energy, is stored in the nucleus of an atom
• Nuclear energy is only released during a
nuclear reaction
• Ex. When a nucleus splits or nuclear power
plants which produce electricity
Thermal Energy
• The total kinetic and potential energy of
particles in an object is called thermal energy
• Thermal energy is known as a type of kinetic
energy
• The higher the temperature of an object, the
more thermal energy the object has.
• Ex. Heating a pot of water. As the heat is
applied to the water, the particles move faster
and the temp. gets hotter
Electrical Energy
• Electrical energy is the energy of electric
charges
• Ex. Getting shocked by metal
• Electrical energy can be either potential or
kinetic energy
Electromagnetic Energy
• Also called radiant energy, is a form of energy
that travels through space in waves
• Examples:
• Light
• Microwaves
• X-ray machines
Chemical energy
• Chemical energy is potential energy
stored in chemical bonds
• Chemical energy is in the food we eat, the
matched we use to light a candle and cells in
out bodies
Energy Transformation &
Conservation
How are different forms of energy
related?
• What does flowing water have to do with
electricity?
• In a hydroelectric power plant, the mechanical
energy of moving water is transformed into
electrical energy.
• ALL FORMS OF ENERGY CAN BE TRANSFORMED
INTO OTHER FORMS OF ENERGY
• A change from one form of energy to another is
called energy transformation.
Single & Multiple Transformations
• Some objects need either a single energy
transformation, while others need multiple.
• Ex. 1: a toaster transforms electrical energy to
thermal energy to toast your bread---that is a
single transformation
• Ex. 2 : A car transforms multiple energies, such
as electrical, thermal, and chemical
Kinetic & Potential Energy
Transformation
• This is the most common transformation.
• Ex. When stretching a rubber band, you give
it elastic potential energy. When you let it go,
the rubber band flies across the room and
has kinetic energy
• Ex. Pendulum
What is the law of conservation of
energy?
• Looking back at the example of the pendulum,
why doesn’t it keep going forever? What
happens to the energy?
• According to the law of Conservation of
Energy, when one form of energy is
transformed to another, no energy is lost in
the process.
• ENERGY CANNOT BE CREATED OR
DESTROYED
What is the law of conservation of
energy?
• As the pendulum swings, it encounters friction
at the top of the string and from the air
through which it moves.
• The kinetic energy then is transformed from
mechanical energy to thermal energy