Transcript Energy and Energy Resources

What is energy?

Energy- the ability to do work
 When one object does work on another object,
energy is transferred from the first object to the
second object.
 The unit for energy is Joule (J)– just like work.
mv2
KE 
2
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Kinetic Energy- energy in motion
All moving objects have kinetic energy
 Kinetic Energy = KE = mv2
2
▪ M = mass (Kg)
v = m/s
▪ Velocity has a greater effect on kinetic energy than mass
does (because it’s squared)

What is the kinetic energy of a car that has a mass of
1,200 Kg and is moving at a speed of 20 m/s?

What is the kinetic energy of a car that has a mass of
2,400 kg and is moving at 20 m/s? How does this kinetic
energy of the car in the above example compare?

What is the kinetic energy of a 4,000 Kg
elephant that is running at 2 m/s? At 4m/s?
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Potential Energy- The energy that an object has because
of the position, shape, or condition of the object

Gravitational Potential Energy - When you lift an object,
you do work on it. When you do this, you transfer
energy to the object and give the object gravitational
potential energy.
 energy stored as a result of position or height.
▪ GPE = weight x height
▪ GPE = Joules (J)
Weight = Newtons (N) height = meters (m)

What is the gravitational potential energy of a book
with a weight of 13 N at a height of 1.5 m off the
ground?

What is the gravitational potential energy of a cat that
weighs 40 N standing on a table that is 0.8 m above the
ground?

What is the gravitational potential energy of
a diver that weights 500 N standing on a
platform that is 10 m above the ground?

Mechanical Energy- the total energy of
motion and position of an object.
 Both kinetic and potential energy are kinds of
mechanical energy
 Mechanical Energy (ME) = potential energy + kinetic energy
(J)
(J)
(J)

What is the mechanical energy of a book being held in
the air that has 100 J or potential energy and 50 J of
kinetic energy?

What is the mechanical energy of a goose standing on a
rock that has 75 J of potential energy and 60 J of kinetic
energy?
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Thermal Energy- is all of the kinetic energy
due to random motion of the particles that
make up an object.

Chemical Energy-The energy in a compound
that changes as its atoms are rearranged

Electrical Energy- is the energy of moving
electrons.
 (negatively charged particles in atoms)

Sound Energy- is caused by an object’s
vibrations.

Light Energy- Produced by the vibrations of
electrically charged particles.

Nuclear Energy- The energy that comes from
the nucleus of an atom.
 Fission and fusion

Friction-A force that opposes motion
between two surfaces that are touching

Closed System- a group of objects that
transfer energy only to each other.
 Energy is conserved, not destroyed.
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Energy cannot be created or destroyed.
The total amount of energy in a closed
system is always the same.
Some energy is always lost to thermal energy
(heat). It’s not lost energy.

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A machine that will run forever without any
additional energy
The machine will put out exactly as much
energy as it takes in.
 This is impossible because waste thermal energy
always occurs due to friction.

Energy Efficiency - is a comparison of the amount of energy
before a conversion with the amount of useful energy after a
conversion

More efficient = less friction/less lost energy