Benchmark Pop Quiz
13, 15, 21, 23, 29
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Monday – Objective #4
18, 27, 44, 46
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Wave
• A wave is any disturbance that transmits
energy through matter or space.
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Medium
• All mechanical waves require a medium through which to
travel.
• The medium is the material through which mechanical
waves travel.
• This type of wave transfers energy by the vibration of particles
in a medium. One particle vibrates and then passes its energy
to a particle next to it. So on and so forth.
• energy is transported throughout the medium, without the
transport of any matter.
WAVE PROPERTIES
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CREST
WAVELENGTH
AMPLITUDE
REST
POSITION
TROUGH
FREQUENCY
CREST – highest point of a wave
TROUGH – lowest point of a wave
WAVELENGTH – distance from peak to peak
AMPLITUDE – the distance a wave rises/falls from its rest position
FREQUENCY – the number of waves passing a given point
HERTZ - how many waves goes by per second
Frequency and Wavelength
Longer wavelengths
result in smaller
frequencies.
Larger frequencies
result in shorter
wavelengths.
As the frequency of a wave increases,
its wavelength decreases.
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Frequency and wavelength are related!
Types of Mechanical Waves
Water Waves
Sound Waves
Seismic Waves
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SOUND
• Sound is a mechanical wave that travels through air at about 340 m/s
or 1100 ft. per second.
• Loud sound waves are greater amplitudes than soft sound waves.
• Loud sounds carry more energy than soft sounds.
• Sound travels faster in a solid than a liquid, and faster in a liquid
than a gas.
• In a sound wave, either the wavelength or frequency determines the
pitch.
• Pitch is the high or low of a sound.
• Sound level (loudness) is measured in units called decibels.
• Vocal cords produce sound by vibration.
• As the frequency of a sound wave increases, its wavelength decreases.
Then there are light waves that require
no medium at all.
They are called electromagnetic waves
TAKE NOTES!
•
Light is a electromagnetic wave that travels through air at about
300,000 km/s.
• Bright lights have greater amplitudes (more energy) than the waves
that make up dim light.
• Because frequency and wavelength are related, either the
wavelength or frequency of a light wave determines the color of
the light. Blue light has a larger frequency and shorter wavelength
than red light. Red light has a shorter frequency and a longer
wavelength.
• Light travels through faster in gases than in solids or liquids.
Example: speed of light is one and a half times faster in air than it is in
glass.
Review
• Waves are the way energy is transferred.
• Waves that travel through a medium are
called mechanical waves and can be water
waves, sound waves, or earthquakes
(seismic waves)
• Waves that do not travel through a medium
are called electromagnetic waves, such as
light, radio waves, and X-rays.
EXAMPLE 2
When a student rides a bike down a hill,
potential energy is transferred into kinetic
energy.
Potential Energy
Kinetic Energy
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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.
Forms of
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Energy is the ability to
cause change
What is Energy?
• An exertion of force
• The ability to do work
• Potential(stored) and Kinetic(motion) a
separate division of each type of energy
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POTENTIAL ENERGY
Energy an object
has because of its
position
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KINETIC ENERGY
• Energy of motion. Only a
moving object has kinetic
energy
• Amount of energy
depends on speed and
mass
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.
TAKE NOTES!
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
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Energy vs. Matter
everything on Earth is either energy or matter
• Energy has no mass or
weight
• Energy does not take up
space
• Energy is NOT
matter
• Matter has mass
and weight
• Matter takes up
space
• Matter is NOT
energy
CONSERVATION of ENERGY – energy can not be
created or destroyed
FORMS OF ENERGY
R
E
C
T
M
N
•
•
•
•
•
•
Radiant – infrared/absorbed
Electrical - power
Chemical - chemicals
Thermal - heat
Mechanical – motion
Nuclear – atoms nuclei
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RADIANT ENERGY
• Energy carried by light and electromagnetic waves is called radiant
energy.
• Light energy travels at a speed of 300,000 km/s.
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ELECTRICAL ENERGY
•energy of electrons
moving along a path
(electrical current/charges)
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CHEMICAL ENERGY
• energy stored in chemical bonds
(when chemicals are broken apart and new molecules are
formed, energy is released)
Each of these items contains
chemical energy.
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THERMAL ENERGY
• energy due to molecular
movement within an object
• increased temperature =
increased thermal energy
• related to temperature of
substance
MECHANICAL ENERGY
Energy created by motion or position.
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NUCLEAR ENERGY
• energy stored in the
nucleus of an atom
The thermal energy given off by the nuclear reaction can be used to heat water to
power an electric power plant.
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 light bulb 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.
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
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. Thermal to mechanical
B. Light to electrical
C. Thermal to chemical
D. Chemical to electrical
Answer: D
Windmill farms are becoming a popular method of
generating electricity for some communities. What
form of energy in wind is used to turn the giant
blades of the windmill?
A. Chemical
B. Mechanical
C. Electrical
D. Thermal
The correct answer is B, Mechanical Energy.
Wind, which turns the windmill blades, is the
movement of air particles.
In a nuclear reactor, the energy used to turn
water into steam is in what form?
A. Chemical
B. Nuclear
C. Electrical
D. Thermal
The correct answer is “D”, thermal energy.
The nucleus of the uranium atom contains
nuclear energy, but this is converted into
thermal energy when the nucleus is split.
The thermal energy is then used to heat the
water to the boiling point.
Nutrients entering muscle cells in the body are converted into
heat. What form of energy is stored in the nutrients?
A. Chemical
B. Nuclear
C. Electrical
D. Thermal
The correct answer is “A”, chemical
energy. Chemical energy is stored
in the chemical bonds of the food
molecules.
RADIATION warms
the surface.
The air near Earth’s surface is
heated by CONDUCTION.
Cooler air pushes warm
air upward, creating a
CONVECTION CURRENTS.
Transfer of HEAT within Earth’s atmosphere.
Methods of Heat Transfer - Energy
Radiation – (rays)
• 30% of the Sun’s rays are reflected back into space
• Transfer of electromagnetic waves
• Transfer of heat energy to an object of lower temperature.
• Ozone layer absorbs ultraviolet radiation
• Is reflected by clouds, surfaces and the atmosphere.
Conduction (touch)
• Is the transfer of energy by fast moving molecules to cooler
molecules - to same temperature.
Convection (currents)
• Caused by density differences in the air.
Simple Machines
•
•
•
•
•
•
Lever
Inclined plane
Wheel and axle
Pulley
Wedge
Screw
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Machines Can…
• Make work EASIER to accomplish (but
amount is the same)
• Change magnitude of force required to
accomplish task
• Change direction of force required to
accomplish task
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Machines Cannot…
• Decrease the amount of work necessary to
accomplish a given task
• Have 100% efficiency
• Run perpetually
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Simple Machines
Levers – is an arm/bar that pivots on a fulcrum
Inclined Plane - a ramp, only one that does not move
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Simple Machines
Wheel and Axle – transfer of energy through the axle to the wheel
Pulley – a wheel with a rope wrapped around it on a fixed axle
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Simple Machines
Wedge – an incline plane that moves using force
Screw – an incline plane wrapped around a cylinder