Benchmark Pop Quiz

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Monday – Objective #4

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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.

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CREST

TROUGH

WAVELENGTH

WAVE PROPERTIESWAVE PROPERTIES

CREST – highest point of a waveTROUGH – lowest point of a waveWAVELENGTH – distance from peak to peakAMPLITUDE – the distance a wave rises/falls from its rest positionFREQUENCY – the number of waves passing a given pointHERTZ - how many waves goes by per second

AMPLITUDE

REST POSITION

FREQUENCY

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Frequency and WavelengthLonger wavelengths Larger frequencies result in smaller result in shorterfrequencies. wavelengths.

As the frequency of a wave increases, its wavelength decreases.

Frequency and wavelength are related!

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Types of Mechanical WavesSound WavesWater Waves

Seismic Waves

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.

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Then there are light waves that require no medium at all.

They are called electromagnetic waves

• 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.

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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.

When a student rides a bike down a hill, potential energy is transferred into kinetic energy.

Potential Energy

Kinetic Energy

EXAMPLE 2

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.

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Forms of

Energy is the ability to

cause change

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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

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

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POSITION 1

POSITION 2

POSITION 3

Potential Energy

Kinetic Energy

Potential Energy

The boulder is in aresting position with low potential energy and no kinetic energy.

EXAMPLE 1

The boulder at the top of the hill has potential energy and no kinetic energy.

As the boulder rolls down the hill, the potential energy transforms into kinetic energy and kinetic energy becomes greater until

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.

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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.

1

2

3

EXAMPLE 4

Explain how energy is transformed as the ball rises and falls.

• Energy has no mass or weight

• Energy does not take up space

• Energy is NOT matter

Energy vs. Mattereverything on Earth is either energy or

matter• Matter has mass and weight• Matter takes up space• Matter is NOT energy

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CONSERVATION of ENERGY – energy can not be created or destroyed

FORMS OF ENERGY• Radiant –

infrared/absorbed• Electrical - power• Chemical - chemicals• Thermal - heat• Mechanical – motion• Nuclear – atoms nuclei

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R

E

C

T

M

N

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)

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Each of these items contains chemical

energy.

THERMAL ENERGY• energy due to molecular movement within an object• increased temperature = increased thermal energy• related to temperature of substance

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MECHANICAL ENERGY

Energy created by motion or position.

NUCLEAR ENERGY• energy stored in the nucleus of an atom

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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.

The boulder would have the greatest kinetic energy at which of the positions on the waterfall?

A

B

A position 1

B position 2

C position 3

D position 4

1

2

3

4

B position 2

QUESTION

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 releasedB At the bottom of the stringC When the yo-yo is fallingD When the yo-yo is climbing the stringA In the hand before the yo-yo is released.

Which will have the most kinetic energy rolling down the hill?

A TruckB BallC RunnerD 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. melting a candle

B. lighting a match

C. solar panels

D. a light bulb

Answer: B

Answer: D

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

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. ChemicalB. NuclearC. ElectricalD. 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. ChemicalB. NuclearC. ElectricalD. 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

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 MachinesLevers – is an arm/bar that pivots on a fulcrum

Inclined Plane - a ramp, only one that does not move

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Simple MachinesWheel 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 MachinesWedge – an incline plane that moves using force

Screw – an incline plane wrapped around a cylinder

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