Energy - isd194 cms .demo. ties .k12. mn .us
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Transcript Energy - isd194 cms .demo. ties .k12. mn .us
Energy
What is Energy?
Energy
The ability to do work.
Work = force x distance
Energy is measured in units called
JOULES which can be abbreviated to J.
Two Types of Energy:
Kinetic and Potential
Kinetic Energy: The energy of an
object that is due to the objects motion.
Kinetic energy = mv2/2
m = mass
v2 = velocity squared
Kinetic Energy Problems
What is the kinetic energy of a car that
has a mass of 2,400 kg and is moving
at 20 m/s?
REMEMBER: mv2/2
m = 2,400 and v = 20 m/s
SO….
2, 400 x 20 x 20/2
You have to multiply by 20 twice due to
velocity being squared!!!
Answer: 4,800,000 Joules (J)
Problem #2
What is the kinetic energy of a 4,000 kg
elephant that is running at 2 m/s?
4,000 x 2 x 2/2
Answer: 8,000 J
Problem #3
What is the kinetic energy of a 2,000 kg
bus that is moving at 30 m/s?
2,000 x 30 x 30/2
Answer: 900,000 J
Final Kinetic Energy Problem
What is the kinetic energy of a 3,000
bus that is moving at 20 m/s?
3,000 x 20 x 20/2
Answer: 600,000 J
Potential Energy and
Gravitational Potential Energy
Potential Energy: energy that an object
has because of the position, shape, or
condition of the object…STORED
energy.
If the object has height the potential
energy is known as GRAVITATIONAL
POTENTIAL ENERGY.
Gravitational Potential Energy
GPE = weight x height
What is the gravitational potential
energy of a cat that weighs 40N
standing on a table that is 0.8 m above
the ground?
40 N x 0.8 m = 32 J
GPE Problem #2
What is the gravitational potential
energy of a diver who weighs 500N
standing on a platform that is 10 m off
the ground?
500 N x 10 m
5000 J
GPE Problem #3
What is the gravitational potential
energy of a diver who weighs 600 N
standing on a platform that is 8 m off the
ground?
600 N x 8 m
4800 J
Mechanical Energy
Mechanical Energy: the total energy of
motion and position of an object
mechanical energy = potential energy =
kinetic energy
Remember that mechanical energy stays the
same unless some of it is transferred to
another object.
Five Forms of Energy
Thermal
Chemical
Electromagnetic (electrical and light)
Sound
Nuclear
Thermal (Heat) Energy
Produced by random motion of particles
that make up the object
Examples: fire, friction, light bulb that
has been on, sun, stove coils
Chemical Energy
Chemical Energy: energy of a
compound that changes as its atoms
are rearranged….a substance changes
into a brand new substance.
Examples: digested food, burning
paper, rusting nail
Electromagnetic Energy
Electromagnetic energy: electrical and
light energy combined….energy of
moving charged particles.
Examples: microwave, amps, sun, light
bulbs, hair dryer, video games
Sound Energy
Sound Energy: energy that vibrating
objects transmits through the air
Examples: vocal chords, guitar strings,
musical instruments
Nuclear Energy
Nuclear Energy: comes from changes
in the nucleus of an atom; most intense
form of energy; dangerous to humans
Examples: sun, nuclear power plants,
nuclear warfare