Transcript What is a wave?

Introduction to Waves
Reporting Category 2
Force, Motion and
Energy
Wave

A wave is any disturbance that transmits
energy through matter or space.
Basic properties of waves :
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
Energy is transferred from one place to another in a wave
motion. (Example: a tidal wave is an energy wave)
Only the shape or form of wave travels, not the substance
it travels through called the medium.
Amplitude (A)

Amplitude – height of
a wave.
Wave Length ()

Wave Length –
distance from one wave
to the next by
measuring:
*crest to crest
*trough to trough
*midpoint to
midpoint
Wave Frequency (f)
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Frequency – The rate
at which the crest
passes a given point.
Unit for frequency is the
Hertz (Hz).
Hertz – how many
waves go by per
second.
Frequency Continued
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High frequency has
short wave length.
Low frequency has long
wave length
Using the Wave Equation
Speed = wave length x frequency
What is a wave?

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It is the way in which energy is transferred
from one place or object to another.
Waves come in various forms.
Waves can travel through a variety of
materials or even empty space.
Waves can do work, sustain life, or cause
great destruction; this occurs when the
energy of the wave is absorbed by matter.
When we think of waves, most of us think about the
beach. These waves travel through water. In this
case, water is called the medium.
The medium can be a gas, such as when
sound travels through the air.
The medium can be a solid, such as when an
earthquake shakes California.
Then there are light waves that require
no medium at all.
They are called electromagnetic waves
Forms
of
Energy is the ability to
cause change
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
THERMAL ENERGY
 energy due to molecular movement within an object
 increased temperature =
increased thermal energy
Which of these objects has more
thermal energy?
CHEMICAL ENERGY
Chemical energy is stored in chemical bonds. When molecules
are broken apart energy is released.
Each of these items contains
chemical energy.
LIGHT ENERGY
 Energy carried by light is called radiant energy.
 Light energy travels at a speed of 300,000 km/s.
ELECTRICAL ENERGY
energy of electrons
moving along a path
(electrical current)
NUCLEAR ENERGY
 energy stored in the
nucleus of an atom
POTENTIAL ENERGY
Energy an object has
because of its
position
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.
Examples of Energy Transformations
Your body converts chemical
energy in food into energy ….
it needs to move,think,grow and heat the body.
What is
temperature?
Moving Molecules
All matter in the Universe is
made of atoms that are on
the move all the time!
How fast atoms move gives us our states of
matter. In a solid, the atoms are tightly
packed together. They cannot change position
easily. They can only vibrate in place. Solids
have a definite shape & definite volume.
In a liquid, the atoms are able to slide past
each other. They can easily change positions
in the liquid. Liquids have a definite volume
but not a definite shape.
In a gas, the atoms are much farther
apart than in solids or liquids. They have
plenty of space to move around in. They
can easily spread throughout all the
space in the container that they are
within. Gases do not have a definite
shape or a definite volume.
Boiling is when heat is added to water in
liquid form (when it’s molecules are moving
very rapidly!) Water vapor (steam) is
produced.
When this occurs, water goes from
the liquid state to the gaseous state.
This is known as VAPORIZATION.
Solidification or freezing is due to a lack
of heat in liquids (when it’s molecules are
moving very slowly!)
Ice and other solid forms of water are
produced when this process takes place.
CONDENSATION is defined as the
conversion of a substance (like water)
from the vapor state to a denser liquid
state that is initiated by a reduction in
temperature of the vapor.
This process is responsible for the
formation of clouds. Condensation is
also a vital component of the water
cycle for clouds then create rain.
Melting is the process by which heat
is added to water (or any liquid
substance) in its solid state such as
ice. The ice then turns into liquid
water.
Force, Speed, and
Motion
How are they related?
Kinds of Force
There are many different kinds of force. There
are pushes
and pulls
electromagnetic forces
weak forces
strong forces
and gravitational forces,
Some forces are referred to as contact forces
and some are non-contact forces
Weight is a type of force
Mass is a measure of how much matter an
object contains.
Weight is the result of the force of gravity
pulling on a mass.
The greater the force of gravity, the greater
the weight.
Acceleration

F=ma is Newton’s 2nd Law and can be
stated: A net force is equal to the mass of the
object times its acceleration. Therefore if
equal force is applied to two objects of
different mass, the smaller mass will
accelerate more
If an object is
traveling at a
constant speed but
is going in a circle,
it is accelerating
because its
direction is
changing
Are these objects accelerating?
Explain.
Newton’s Second Law
Little Acceleration
Little Force
Same Mass
Big Force
Big Acceleration
Small Mass / Big Acceleration
Same Force
Big Mass / Small Acceleration
Simple Machines
Levers
Inclined Plane
Simple Machines
Wheel and Axle
Pulley
Simple Machines
Wedge
Screw
Machines Cannot…
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Decrease the amount of work necessary to
accomplish a given task

Have 100% efficiency
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Run perpetually
Machines Can…
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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
Forces related to basic processes
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Blood flow in the body
Plate movement (tectonics)
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–
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Volcanic eruptions
Earthquakes
Mountain building
Emergence of seedlings
Erosion
Blood Flow
Volcanic Eruptions
Hilo, Hawaii
Mountain Building
Emergence of Seedlings
Erosion
Check your understanding
1. How do the wave lengths compare for two
waves traveling at the same speed with
frequencies in a ratio of 2 to 1?
A)
B)
C)
D)
2:1
1:2
4:1
1:4
http://www.glenbrook.k12.il.us/gbssci/phys/Class/waves/u10l2e.html
2.
The boulder would have the greatest kinetic energy at
which of the positions on the waterfall?
A position 1
B position 2
C position 3
D position 4
1
4
2
B
3
3.
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
4. Which of the following is an example of a
wave?
a. erosion
b. an earthquake
c. a volcano
d. a glacier
5. 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
6. In a nuclear reactor, the energy used to turn
water into steam is in what form?
A. Chemical
B. Nuclear
C. Electrical
D. Thermal
7. Which of the following can be used to transform
chemical energy into heat energy?
A. melting a candle
Answer: B
B. lighting a match
C. solar panels
D. light bulb
8.
When the human heart contracts, it pumps
blood to other parts of the body. When the
heart contracts, the blood moves because the-
A.
B.
C.
D.
Pressure to the heart increases
Temperature of the blood increases
Density of the blood increases
Size of the heart increases
9.
As a lima bean seedling starts to grow
into the soil the root tip is able to push
through the soil because it acts as a -A.
B.
C.
D.
Wheel
Pulley
Gear
Wedge
10. Which force causes the water to
move downstream?
A.
B.
C.
D.
Gravitational
Chemical
Electrical
Solar
11. Which of the following describes the motion of
the runner?
A The runner is moving at a
constant rate
B The runner is moving slower at
the end
C The runner is speeding up
D The runner’s speed was a
constant 4 m/s