Transcript Spring Semester Exam Notes Cliff Notes

Spring Semester Exam
Cliff Notes
May 2009
1
•
Parts
Scientific Method
1. Problem- What is it that you are trying to find out.
2. Research- Find out background information about the
topic.
3. Hypothesis- Educated Guess
4. Experiment- Testing your hypothesis
1. Control- Thing you do not change in the experiment to use for
comparison.
2. Independent Variable- Something in the experiment that the
investigator changes on purpose.
3. Dependent Variable- The thing that changes because of the
Independent Variable
4. Constant- Things you keep the same in the experiment to control
the results and ensure accurate data.
5. Data- Tables, Graphs, and Charts of your experiments
results.
6. Conclusion- Summary of results of experiment and tell
whether your hypothesis is correct or not.
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Graphing Rules
•
•
Determine the best “axis “for each variable.
– The manipulated variable (independent variable) is always placed on the
horizontal (x) axis
– The responding variable (dependent variable) is always placed on the vertical
(y) axis.
Label each axis and don’t forget to include units (ex. grams, mL, minutes, etc.).
3 main types of graphs:
– Line Graph
– Bar Graph
– Pie Chart
• Line Graph: a graph in which points representing values of a variable for suitable
values of an independent variable are connected by a broken line.
– Used to compare rates such as distance and time or Independent Variable
versus Dependent Variable.
• Bar Graph (Bar Chart): a graphic means of quantitative comparison by rectangles
with lengths proportional to the measure of the data or things being compared.
– Used when measuring categories such as a poll of peoples favorite colors or
favorite kind of ice cream.
• Pie Chart (Circle Graph): a circular chart cut by lines into segments illustrating
relative magnitudes or frequencies as PERCENTAGES.
– Used to show quantitative comparisons of different categories as percentages.
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(The same type of information as a bar graph but show in percentages.)
Accuracy vs. Precision
• Accuracy- degree of closeness of a measurement
or aim.
– When you measure something and you try to get as close
to the true weight as possible. The ore decimals you have
in your answer the closer or more accurate you are.
• Precision- the ability of a measurement to be
reproduced consistently.
– If you do an experiment over and over and you get the
same results each time then the results are precise.
• You can be accurate but not precise, precise but not
accurate, or both precise and accurate at the same
time.
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Density, Buoyancy, Viscosity
• Buoyancy- is the ability of a fluid (liquid or gas) to
exert an upward force on an object immersed in it.
– Ex. The water exerting an upward force on a ship.
• Viscosity- The resistance of a fluid to flow
– High viscosity, liquid flows slowly (Ex. Corn syrup)
– Low viscosity, liquid flows fast (Ex. Water)
• Density- how heavy or light an object is.
–
–
–
–
High density, heavy object (Ex. Brick)
Low density, light object (Ex. Feather)
Units: g/cm3 or g/ml
Formula: Density = mass/ volume
d= m
v
m
d
v
X
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Energy Resources
• Renewable- Resources that renew
themselves over time quickly.
– Wind, Hydroelectric (electricity from water), Solar
(Sun), Geothermal (heat from earth), and Nuclear
• Nonrenewable- A limited resource that takes a
long time to replace. Once it is gone it is
gone.
– Petroleum, Natural Gas, Coal, Fossil Fuels
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•
•
Energy
Energy- the ability to cause change or do work.
–
All energy is measured in Joules (J).
Law of Conservation of Energy- Energy can not be created or destroyed it can only be converted
from one form of energy to another.
–
The total amount of energy in the universe remains the same!
7 Forms of Energy
•
Nuclear- energy trapped inside atoms. This energy holds parts of the nucleus of an atom together.
Ex: bombs
•
Light- energy that passes through space in the form of waves. Light is always in motion and
cannot be stored, so it is a type of kinetic energy. Ex: sunlight
•
Sound- Energy of vibrating particles. Ex: music, sirens
•
Electrical- Energy from moving electrons. Ex: electricity running a blow dryer
•
Heat (Thermal)- The internal motion of atoms). Heat is due to the kinetic energy or the motion of
atoms or molecules in a substance. As this motion increases, the temperature also increases. The
hotter the substance is, the faster the particles vibrate. Ex: heat released from your body that
causes sweat.
•
Mechanical (Kinetic and Potential)- things in motion. Ex: rollercoaster, engine in a car
•
Chemical- Chemical energy bonds atoms or ions together. Chemical energy is food energy. Ex:7
digesting food, photosynthesis
Kinetic and Potential Energy
• Kinetic Energy (KE)- energy in motion. The object has
to be moving to have kinetic energy. Units: Joules (J)
KE= mass x velocity2
2
KE= m x v2
2
• Potential Energy (PE)- stored energy. The higher the
object is from the ground the more potential energy.
Units: Joules (J)
PE= mass x gravity x height
g= 9.8 m/s2
PE= m x g x h
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Heat Transfer
• Heat ALWAYS travels from HOT to COLD.
• Conduction- Transfer energy in solids through direct
contact (do not move but pass energy along).
– Ex: frying a pork chop in a skillet. Must touch skillet to fry!
• Convection- Transfer energy in liquids and gases by
particles moving from place to place. Hot liquids and
gases rise. Cold liquids and gases fall.
– Ex: heater heating a room.
• Radiation- Transfer energy via electromagnetic waves.
No matter required. When radiant energy strikes a
material the energy can be absorbed, reflected, or
transmitted.
– Ex: heat from the sun warming earth.
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Speed
- How fast an object is going in a certain amount
of time.
Velocity- speed and velocity are the same except
velocity tells direction also.
• Velocity (Speed) is measured in meters per
second, m/s, or mph, or km/hr
• Formula: v = d/t, velocity = distance/time
d
v
t
X
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Acceleration
•
Acceleration is the change in velocity over time: Rate of change of velocity
•
It can be a change in speed, a change in direction or in both speed and direction.
•
The unit of acceleration is m/s2 (meter per second square)
•
Acceleration can be:
– Positive: the object is speeding up
– Negative: the object is slowing down, called deceleration.
•
When there is no acceleration (zero acceleration): the object is at rest or the
object is moving at a constant velocity
• Equation: vf –
vi
t
vf= ending speed
vi= starting speed
t= time
vf-vi
a
t
X
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Momentum
• A property of a moving object that depends on the
object’s mass and its velocity.
– The bigger the object the more momentum
– The faster the object the more momentum
• If an object is not moving (velocity = 0), its’
momentum is zero.
• Law of Conservation of Momentum- momentum
isn’t created or destroyed but transferred from object
to object.
• Momentum = mass x velocity
p=m x v
• Units: g x m/s
p
m
v
X
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Forces
• Balanced forces – forces on an object that are Equal in size
and Opposite in direction.
• Unbalanced forces – forces that are NOT balanced by
another force. Causes an object to be put into Motion. The
object will move in the direction of the greater force.
• Gravity- unseen downward force acting on everything all the
time. g= 9.8 m/s2
– The bigger the object the more gravitational force (pull). The bigger
the object the more gravitational force (pull).
– The closer the objects the greater the gravitational force.
• Friction- unseen force between two objects that touch acting
to slow the moving object down. It also produces heat.
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Newton’s Laws
• 1st Law (A.K.A- Law of Inertia)
– An object in Motion will remain in Motion; An object at Rest
will remain at Rest, until acted upon by another Force.
– Inertia- the tendency of an object to resist any change in its
Motion.
• 2nd Law
– If you apply a Force to a Mass it will Accelerate.
– Force = Mass x Acceleration F= m x a
– Units: Force= Newtons (N), Mass= grams (g),
Acceleration= m/s2
•
3rd Law
F
m
a
X
– For every Action there is an equal and opposite Reaction!
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•
Waves
a repeating disturbance or movement that transfers ENERGY through
space or matter.
– Matter is NOT transferred, Energy is transferred!
– Waves are produced by something vibrating.
• 2 Types of Waves:
– Mechanical (require a medium, ex: water and sound) and
– Electromagnetic (no medium, travel through outer space, ex: light)
• Frequency (f)- number of waves that pass a point per second. Units:
Hertz (Hz)
• Amplitude- How high or low the wave moves from the resting position.
• Wavelength (λ)- the distance from a point on one wave to the same point
on the next wave. (Space between waves). Units: meters (m)
• Wave speed- how fast the wave travels. Units: m/s
– Formula: wave speed = frequency x wavelength
v=fxλ
v
λ15
f
X
Mechanical Waves
• Transverse- Particles of the medium vibrate
perpendicular (up & down) to the direction
the wave is moving
– Ex: water
• Longitudinal- Particles in the medium travel
back and forth n the same direction that the
wave travels.
– Ex: sound
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Parts of Waves
• Transverse
Crest
Amplitude
NODAL LINE
Resting position
Wavelength
Trough
• Longitudinal (Compression)
Compression
Wavelength
Rarefaction
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Sound Waves
• Resonance- is the ability of an object to vibrate
by absorbing energy at its natural frequency
– Ex. A “singing” wine glass and musical
instruments
• Doppler Effect- When the vibrations of a sound
wave are coming towards you, the waves are
close together (compressed). When the source
passes you, the waves are farther apart.
– This explains why the sound of an
ambulance siren has a high pitch
(frequency) as it is moving towards
you and a low pitch (frequency) once
it passes you and moves away.
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Reflection
- the bouncing back of a wave
Ex: Your reflection in a mirror
Refraction
-the bending of a wave caused by a change in
speed of the wave as it passes from one medium
to another.
Ex. Objects look distorted
under water or farther away
than they really are.
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DIFFRACTION
The bending
of a wave as it passes
an edge or opening
EXAMPLE: Ocean waves change
direction and bend after striking
an island
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Interference
The combination of 2 or more waves
• Constructive Interference- occurs when
waves align in sync and are added together
– Ex. in sound waves constructive interference
causes a louder sound
• Destructive Interference- occurs when
sound waves are out of sync. They subtract
from each other.
– Ex. in sound waves destructive interference
causes a softer sound
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Electricity
- Electricity is the flow of electrons (negative particles) from
one place to another.
- Current (I)- is a measure of the amount of charge (or energy)
transferred over a period of time.
- Unit: Ampere (A)
- Resistance (R)- when one force slows down or gets in the
way of another force. The tendency for a material to oppose
the flow of electrons.
- Unit: Ohms (Ω)
- Voltage (V)- What makes current flow
V
- Units: Volts (V)
Equation: Current = Voltage/ Resistance
I
I=V/R
R
X
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Circuits
• Electric Circuit - an electrical device connected so that it
provides one or more complete paths for the movement of charges.
– In other words, an electric circuit is a path through which charges can be
conducted.
• Series Circuit - describes a circuit or portion of a circuit that
provides a single conducting path. In other words, it has only one
path for current to follow.
• Parallel Circuit- describes components in a circuit that are
connected across common points, providing two or more separate
conducting paths. In other words, they contain many separate
paths for the current to follow.
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Magnets
• Magnets- Magnetism is a property of matter that
causes materials to exert forces on one another.
– Magnetic poles produce magnetic forces. Forces are
strongest at the poles.
– The space around a magnet is filled with a magnetic field.
– A magnetic field is an area in space that exerts magnetic
force.
• Electromagnets- is a current-carrying coil behaving
like a magnet. An electric charge in motion (current)
produces a magnetic field.
– The direction of the magnetic field depends on the
direction of the current.
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Work and Power
• Work (W)- is always something done by a force on an object,
changing the motion of the object.
– Units: Joules (J)
– Work= Force x distance
W
W= F x d
• Force (Newtons); distance (meters)
F
d
X
– Efficiency (E)- a quantity (expressed as a percent) that measures the ratio of
useful work output to work input.
• The amount of work obtained from a machine is ALWAYS less than the amount of
work put into it. This is because some of the work is lost due to friction in the
form of heat.
• Formula: % Efficiency = work output X 100
work input
*** There is no unit for Efficiency. Use a percent (%) sign.
• Power (P)- is the amount of work done in a certain amount of time.
– Units: Watts (W)
– Power = Work/Time
P= W/t
W
• Work (joules); times (seconds)
P
t
X
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Simple Machines
• Any instrument that makes work easier by
doing work with only one movement.
Machines
• 6 Types:
– Levers
– Pulleys
Simple
Compound
– Inclined Planes
– Wheel and Axle
Incline Plane
Lever
– Screw
Family
Family
– Wedge
• 2 Families: Levers and Inclined Plane
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6 Types of Simple Machines
1.
Levers- A bar or rigid arm that turns around a fixed point called the
fulcrum. Three classes of lever 1st-3rd. Ex: scissors
2.
Pulleys- A modified lever that helps raise objects. A single pulley
changes the direction of the force. Ex: flag poles
3.
Inclined Planes- A flat surface that elevated at one end. Decreasing
the amount of force you have to apply, but increases the distance you
have to apply it. Ex: ramps, stairs
4.
Wheel and Axle- Made of a pulley (the wheel) connected to a shaft (the
axle). Multiplies the force. When a small force is applied to the wheel,
a large force is produced by the machine. Small force in; large force
out. Ex: door knob, steering wheel
5.
Screw- An inclined plane wrapped around a post to form a spiral.
Decreases the amount of force you apply, but increases the distance.
Ex: jar lid
6.
Wedge- A type of inclined plane that moves. Changes the direction of
the force. Turns one force into two forces directed out to the sides.27
Ex: knife, axe
Mechanical Advantage
• How much stronger the machine makes you.
• Formula: MA = Output FORCE
input FORCE
MA = Input DISTANCE
output DISTANCE
Telling the MA of…
Length
Height
(input)
(output)
• Inclined Planes- length/height
• Pulleys- count the number of ropes pulling up.
• Levers- Output side is the end that has your load
(what you are DOING the work on). Input side is the
end where YOU put in the work.
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Gas Laws
• Charles Law- if temperature increases so does volume.
Temperature = Volume
Temperature = Volume
• Boyles Law- Boyle’s Law says if the pressure goes up the
volume goes down in a closed container at constant
temperature.
Pressure = Volume
Pressure = Volume
• Pascal Law- Pascal’s principle states that pressure
applied to a fluid (liquid or gas) is transmitted throughout
the fluid.
– Ex. Squeezing a balloon, or tube of toothpaste…the pressure
applied to the fluid is transmitted through the fluid air or fluid
toothpaste
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