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ENERGY
Essential Question: What is Energy?
AIM: SWBAT define the word “energy” and describe
examples of energy.
What is Energy?
• Most central concept underlying science
• Comes in many forms
• Transforms from one form to another
• Difficult to describe
• Defined as the ability to do work
• Like work, it is measured in Joules
When something or somebody moves or jumps or falls or
explodes or breathes or thinks or dances or does anything, it's
because energy is being transformed.
Work
Work is the transfer of energy through motion. In
order for work to take place, a force must be exerted
through a distance. The amount of work done
depends on two things: the amount of force exerted
and the distance over which the force is applied.
There are two factors to keep in mind when
deciding when work is being done: something has to
move and the motion must be in the direction of the
applied force. Work can be calculated by using the
following formula: Work=force x distance
Types of Energy
Kinetic Energy:
1. the energy
contained in a
moving mass or in
a moving particle
2. The conversion
of this capability
to motion
Potential Energy
is 1.stored energy
or energy waiting
to happen.
2. The capability of
doing work.
Radiant Energy
Radiant energy is also called electromagnetic energy.
Radiant energy is the movement of photons. All life on earth
is dependent on radiant energy from the sun. Examples of
radiant energy include radio waves (AM, FM, TV),
microwaves, X-rays, and plant growth.
Forms of
Energy
Chemical Energy
Chemical energy is the energy
stored in the bonds of atoms and
molecules. This a form of
potential energy until the bonds
are broken. Fossil fuels and
biomass store chemical energy.
Products that contain chemical
energy include: TNT, baking soda,
and a match. Biomass, petroleum,
natural gas, propane and coal are
examples of stored chemical
energy.
Forms of
Energy
Electrical Energy
Electrical energy is the
movement of elections.
Lightning and static
electricity are examples of
electrical energy that occur
naturally. Electric energy
can also be stored in manmade sources like batteries.
Forms of
Energy
Nuclear Energy
Nuclear energy is the
energy stored in the nucleus
of an atom. Nuclear energy
is unusual in that it can give
off energy in the form of
light or heat, but it is the
change in the atom's
makeup that produces the
energy. Submarines, power
plants, and smoke detectors
all use nuclear energy.
Forms of
Energy
Thermal Energy
Thermal energy or heat energy
is the internal energy in
substances. Heat or thermal
energy comes from the vibration
and movement of atoms and
molecules within substance.
Examples; Boiling water,
burning wood, and rubbing your
hands together really fast.
Forms of
Energy
Mechanical Energy
Mechanical energy is the
movement of machine parts.
Mechanical energy is also the
total amount of kinetic and
potential energy in a system.
Examples: Wind-up toys and
grandfather clocks.
Potential energy + Kinetic energy = Mechanical
energy
Revisit: Potential Energy
• Stored energy - the potential for doing work
• Depend on the position and condition of the object.
• Think of a stretch rubber band on a slingshot, it has
potential energy due to his position. If the rubber band
was placed in a slingshot, it is capable of doing work.
Gravitational Potential Energy
• Potential Energy due to elevated positions
• GPE of an object is equal to the work done against gravity
in lifting it.
• Gravitational potential energy = weight times the height
GPE = mgh
Calculating GPE
• Calculate the change in potential energy of 8 million kg
of water dropping 50 m over Niagara Falls.
Calculating GPE
• Given: m= 8 million
h = 50 m
g = 9.8 m/s2
• Image:
• Relationship: GPE = mgh
• Looking For: Gravitational Potential energy in Joules
• Solution:
GPE = mgh
=(8,000,000 kg)(9.8 m/s2)(50 m)
= 3,920,000,000 J or 3.92 x109 J
Revisit: Kinetic Energy
• Energy of motion
• Depends on the mass and velocity of the object
• A moving object is capable of doing work
• Kinetic energy = 1/2 mass times the velocity squared.
KE = 1/2 mv2
• KE = to the work required to bring the object to that speed
from rest, or the work the object can do while being
brought to rest
Fd = 1/2 mv2
Calculating KE
• Calculate the kinetic energy of a 3-kg toy cart that
moves at 4m/s.
Calculating KE
• Given : m = 3kg
v = 4 m/s
• Image:
v = 4 m/s
m = 3 kg
• Relationship: KE = 1/2 mv2
• Looking for: KE in Joules
• Solution: KE = 1/2 mv2
= 1/2 (3-kg)(4 m/s)2
= 1/2 (3-kg)(16 m2/s2)
= 1/2 (48 kg.m2/s2)
= 24 kg.m2/s2 or 24 Joules
Law of Conservation of Energy
• It states that: Energy cannot be created or destroyed. It
is transformed from one form into another, but the total
amount to energy never changes.
• Example - When gasoline combines with oxygen in a
car’s engine, the chemical PE stored in the fuel is
converted to Molecular KE, or thermal energy. Some of
this energy is transferred to the piston and some if this
energy causes the motion of the car.
Works Cited
• Maslow, G.(2011). Energy [PowerPoint slides]. Retrieved
from http://www.dropbox.com/