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Spring Semester ExamCliff Notes

May 2009

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Scientific Method• Parts

1. Problem- What is it that you are trying to find out.2. Research- Find out background information about the

topic.3. Hypothesis- Educated Guess4. 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.

(The same type of information as a bar graph but show in percentages.)

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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

X

m

d v

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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: digesting food, photosynthesis

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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 KE= m x v2

2 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 PE= m x g x h

g= 9.8 m/s2

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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 When radiant energy strikes a material the energy can be absorbed, reflected, or material the energy can be absorbed, reflected, or transmitted.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/timev t

d

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

tvf= ending speedvi= starting speedt= time

a t

vf-vi

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 X

vm

p

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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– For every Action there is an equal and opposite Reaction!

X

F

m a

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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 = f x λX

f

v

λ

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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

• Longitudinal (Compression)RarefactionCompression

Wavelength

Crest

Wavelength

Trough

Amplitude

NODAL LINE Resting position

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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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Ex: Your reflection in a mirror

Reflection- - the bouncing back of the bouncing back of a wavea wave

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 bendingof a wave as it passesan edge or opening

EXAMPLE: Ocean waves change direction and bend after striking an island

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InterferenceThe 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 - Units: Volts (V)

Equation: Current = Voltage/ Resistance I=V/RX

V

I R

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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= F x d

• Force (Newtons); distance (meters)

– 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

• Work (joules); times (seconds)

X

W

F d

X

W

P t

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Simple Machines• Any instrument that makes work easier by

doing work with only one movement.

• 6 Types:– Levers– Pulleys– Inclined Planes– Wheel and Axle– Screw– Wedge

• 2 Families: Levers and Inclined Plane

Machines

Simple Compound

Lever Family

Incline Plane Family

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6 Types of Simple Machines1. 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. Ex: knife, axe

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Mechanical Advantage• How much stronger the machine makes you.• Formula: MA = Output FORCE

input FORCE

MA = Input DISTANCE

output DISTANCE

Telling the MA of… • 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.

Length (input)Height

(output)

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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