Transcript Motion, Forces and Energy

Motion, Forces and Energy
Energy transformations found in everyday life will be emphasized.
Students should know that an object at rest has potential energy
and an object in motion has kinetic energy. Students should also
understand that energy transformations occur in energy
production, as in the conversion of wind energy to electrical
energy.
KEY TERMS
•
An energy transformation occurs when
energy changes from one form to
another.
•
Energy transformations occur in energy
production (as in conversions of energy
for use in everyday life).
•
Potential Energy is the energy that is
stored because of an object’s position.
•
The energy of an object due to its
motion is called Kinetic Energy.
EXAMPLE 1
POSITION 1
Potential Energy
The boulder at the
top of the hill has
potential energy
and no kinetic
energy.
POSITION 2
Kinetic Energy
Potential Energy
As the boulder rolls
down the hill, the
potential energy
transforms into kinetic
energy and kinetic
energy becomes
greater until
POSITION 3
The boulder is in a
resting position with
low potential energy
and no kinetic
energy.
EXAMPLE 2
When a student rides a bike down a hill,
potential energy is transferred into kinetic
energy.
Potential Energy
Kinetic Energy
The amount of kinetic energy also depends on
the mass and the speed of an object.
Kinetic energy increases as speed increases.
The faster an object moves, the more kinetic
energy it has.
EXAMPLE 3:
The faster a bowling ball
moves, the harder it will
strike the pins, the more
pins it can knock down.
As the ball leaves the ground, it is moving the fastest and
has the maximum kinetic energy. As the ball moves upward,
it slows down as it’s kinetic energy is transformed into
potential energy. As the ball moves downward, it speeds up
as its potential energy is transformed into kinetic energy.
2
EXAMPLE 4
Explain how energy is
transformed as the ball rises
and falls.
1
3
QUESTION
The boulder would have the greatest kinetic energy at which
of the positions on the waterfall?
A position 1
A 1
B position 2
C position 3
4
2
D position 4
3
B
position 2
B
A yo-yo can demonstrate both Potential and
Kinetic energy.
When does a yo-yo have it greatest potential
energy?
A In the hand before the yo-yo
is released
B At the bottom of the string
C When the yo-yo is falling
D When the yo-yo is climbing
the string
A
In the hand before the yo-yo is released.
Which will have the most kinetic energy
rolling down the hill?
A Truck
B Ball
C Runner
D All of the are examples of Potential
energy.
Answer: A
Examples of Energy Transformations
Your body converts chemical
energy in food into energy ….
it needs to move,think,grow and heat the body.
Examples of Energy Transformations
An electric current that flows in a wire
carries electrical energy that can be used in
many ways.
A stove transforms
electrical energy to heat
energy that boils the water
and cooks food.
A lightbulb converts
electrical energy into light
energy when you flip a
switch.
Examples of Energy Transformations
The most common windmills convert
the kinetic energy of the wind into
rotary motion of the generator. The
rotating generator, typically a
direct-drive permanent magnet
alternator, produces electricity.
The chemical fuel is transformed
into thermal and mechanical energy
needed to run the car.
Which of the following can be used to transform
chemical energy into heat energy?
A.
B.
melting a candle
lighting a match
C.
solar panels
D. a light bulb
Answer: B
Which of these types of energy conversions
occurs in a battery-powered flashlight?
A.
A. Thermal to
mechanical
B. Light to
electrical
C. Thermal to chemical
D. Chemical to electrical
Answer: D