Yr 9 Work Power Energy Revision

8/14/2019 Yr 9 Work Power Energy Revision

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EDEXCEL IGCSE / CERTIFICATE IN PHYSICS 4-3

Work and PowerEdexcel IGCSE Physics pages 142 to 149

June 17 th 2012

All content applies for Triple & Double Science


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Edexcel SpecificationSection 4: Energy resources and energy transfer c) Work and powerknow and use the relationship between work, force and distance moved in thedirection of the force:work done = force distance moved W = F d understand that work done is equal to energy transferredknow and use the relationship:gravitational potential energy = mass g heightGPE = m g h know and use the relationship:kinetic energy = mass speed 2 KE = m v 2

understand how conservation of energy produces a link between gravitationalpotential energy, kinetic energy and workdescribe power as the rate of transfer of energy or the rate of doing workuse the relationship between power, work done (energy transferred) and timetaken:power = work done / time taken P = W / t


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Work and energyWhen a force causes a body to move through a distance,

energy is transferred and work is done.

work done = energy transferred.

Both work and energy are measured in joules (J).


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Work and frictionWork done against frictionalforces is mainly transformed intoheat.

Rubbing hands together causesthem to become warm.

Brakes pads become hot if theyare applied for too long. In thiscase some of the cars energymay also be transferred to soundin the form of a squeal


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The work equation

work done = force applied distance moved inthe direction ofthe force

W = F x d

work, W is measured in joules (J)

force, F is measured in newtons (N)distance, d is measured in metres (m)


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Question 1

Calculate the work done when a force of 5Nmoves through a distance of 3m.

W = F x d = 5N x 3mwork = 15 J


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Question 2

Calculate the work done when a force of6N moves through a distance of 40cm.

W = F x d = 6 N x 40 cm= 6 N x 0.40 m

work = 2.4 J


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Question 3

Calculate the value of the force required todo 600J of work over a distance of 50m.

W = F x d becomes: F = W d

= 600 J 50 mforce = 12 N


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Question 4

Calculate the distance moved by a force of8N when it does 72J of work.

W = F x d becomes: d = W F

= 72 J 8 Ndistance moved = 9 m


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Question 5Calculate the work done bya child of weight 300N whoclimbs up a set of stairsconsisting of 12 steps eachof height 20cm.

W = F x d

The child must exert anupward force equal to its

own weight.Therefore: force = 300N

This force is exertedupwards and so thedistance must also bemeasured upwards.= (12 x 20cm)

= 2.4mtherefore: work = 300 N x 2.4 m

work = 720 J


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Question 6Calculate the work done by a person of mass 80kg whoclimbs up a set of stairs consisting of 25 steps each ofheight 10cm.

W = F x d the person must exert an upward force equal their weightthe persons weight = (80kg x 10N/kg) = 800N the distance moved upwards equals (10 x 25cm) = 2.5mwork = 800 N x 2.5 mwork = 2000 J


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Completework force distance

J 50 N 3 m

800 J N 20 m

500 J 250 N m

kJ 4000 N 2 m

2 MJ 3.03 N 5 km

150

40

2

80

400

Answers


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Choose appropriate words to fill in the gaps below:

Work is done when a _______ moves through a distance.

The amount of _______ transferred is also equal to the workdone. When a car brakes energy is transformed to ______.

Work done is ______ to the force _________ by the distancemoved in the __________ of the force. The work done ismeasured in ______ if the force is measured in newtons andthe _________ in metres.

multiplied distance joulesequalforceenergy direction

WORD SELECTION:

heat

multiplied

distance

joules

equal

force

energy

direction

heat


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Gravitational potential energyGravitational potential energy (GPE) is the energy storedin an object when work is done in moving the objectupwards.

GPE = mass x g x heightGPE = m x g x h

GPE is measured in joules (J)mass, m is measured in newtons (N)gravitational field strength, g is measured

in newtons per kilogram (N/kg)height, h is measured in metres (m)


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Question 2

Calculate the gravitational potential energygained by a student of mass 70kg climbing aflight of stairs of height 4m.

GPE = m x g x h = 70kg x 10N/kg x 4m

GPE = 2 800 J


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Question 1Calculate the kinetic energy of a car of mass1000kg moving at 5 m/s.

K E = x m x v 2 = x 1000kg x (5m/s) 2

= x 1000 x 25= 500 x 25kinetic energy = 12 500 J


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Question 2

Calculate the kinetic energy of a child of mass60kg moving at 3 m/s.

K E = x m x v 2 = x 60kg x (3m/s) 2

= x 60 x 9= 30 x 9kinetic energy = 270 J


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Question 3

Calculate the kinetic energy of a apple of mass200g moving at 12m/s.

K E = x m x v 2

= x 200g x (12m/s) 2= x 0.200kg x 144= 0.100 x 144

kinetic energy = 14.4 J


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Question 4Calculate the mass of a train if its kineticenergy is 2MJ when it is travelling at 4m/s.

K E = x m x v 2

2MJ = x mass x (4m/s) 22 000 000J = x mass x 162 000 000 = 8 x mass

2 000 000 8 = mass mass = 250 000 kg


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Question 5Calculate the speed of a car of mass 1200kg if itskinetic energy is 15 000J.

K E = x m x v 2 15 000J = x 1200kg x (speed) 2

15 000 = 600 x (speed) 2 15 000 600 = (speed) 2

25 = (speed) 2

speed = 25speed = 5 m/s


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Question 6Calculate the speed of a ball of mass 400g if itskinetic energy is 20J.

K E = x m x v 2 20J = x 400g x (speed) 2

20 = x 0.400kg x (speed)2

20 = 0.200 x (speed) 2 20 0.200 = (speed) 2

100 = (speed) 2

speed = 100speed = 10 m/s


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Completekinetic energy mass speed

J 4 kg 2 m/s

27 J kg 3 m/s

1000 J 80 kg m/s

kJ 200 kg 8 m/s

3.2 J 3.03 g 4 m/s

8

6

5

6.4

400

Answers


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Falling objectsIf there is no significant airresistance then conservationof energy results ingravitational potential energybeing converted into kineticenergy as an object falls.

gain in KE = loss of GPE

h

m

h

v 1

v 2

gpe = m gh

k e = m v 2

2

k e = 0

gp e = 0

gp e = ke

g p e = m g hk e = m v 1 2

ke = m gh


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Graphs of GPE and KE

E n e r g y

Time0

0objectdropped

GPE

KE

TOTAL ENERGY = GPE + KE

object reacheslowest point


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Question A child of mass 40kg climbs awall of height 3m and thensteps off. Calculate the speedat which the child reaches thebottom of the wall.

Childs initial gravitationalpotential energy:GPE = m x g x h = 40kg x 10N/kg x 4mGPE = 1 600 J

If air resistance is insignificantthen all of this GPE is convertedinto kinetic energy

K E = x m x v 2

1600 J = x 40kg x (speed) 21 600 = 20 x (speed) 2 1 600 20 = (speed) 2 80 = (speed) 2

speed = 80

speed = 8.94 m/s


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Gravitational ________ energy is the energy stored when an

object is lifted ________. This energy is released when theobject _____ back to its initial position.

Kinetic energy is the energy possessed by an object due to its _______ and mass. If the mass of an object is ________ its

kinetic energy doubles. If the speed is doubled the kineticenergy will increase by ______ times.

When a __________ object is released gravitational potentialenergy is converted into _________ energy.

doubledkinetic raisedfalls potential upwardsfour

WORD SELECTION:

speed

doubled

kinetic

raised

falls

potentialupwards

four

speed


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Power ( P )Power is a measured of how quickly work is done.

pow er = wo rk don et im e taken

P = Wt

power, P is measured in watts (W)work done, W is measured in joules (J)time, t is measured in seconds (s)

One watt is the same as one joule per second .


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Power is also equal to how quicklyenergy is transformed from one form toanother.

po w er = energy c hang e

t imeP = E

t


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Question 1Calculate the power of a motor that exerts a force

of 40N over a distance of 2m for 10seconds.

W = F s= 40 N x 2 m

work done = 80 J

P = W / t = 80J / 10 spower = 8.0 W


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Question 2Calculate the power of anelectric motor that lifts amass of 50 kg upwards by3.0 m in 20 seconds.

g = 10 N/kg

gain in GPE = m g h= 50 kg x 10 N/kg x 3 m= 1500 J

P = E / t = 1500 J / 20 spower = 75 W


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Complete:energy

transferwo rk don e t im e power

600 J 600 J 120 s 5 W

440 J 440 J

20 s 22 W28 800 J 28 800 J 2 hours 4 W

2.5 mJ 2.5 kJ 50 s 50 W

Answers

600 J 5 W

440 J 20 s28 800 J 28 800 J

2500 J 50 W


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Measuring a persons power 1. Measure the weight, W ofperson using weighing scales.

2. Measure the time taken forthe person to run up a flight ofstairs of height, h

3. Work done= weight x height= W x h= W x n x s

4. Power of the person= work done / time taken= ( W x n x s ) / t

total stairsheight, h

= n x sstairs

of n steps

s

person ofweight, W


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Example calculationWeight of person, W = 800NTime taken, t = 3.0 seconds

Stairs:number of steps, n = 12height of step = 0.20mtotal stair height, h = 12 x 0.20m = 2.4m

Work done= weight x height= 800N x 2.4m = 1920J

Power = 1920J / 3.0s= 640W

total stairsheight, h

= n x sstairs

of n steps

s

person ofweight, W


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Power is a measure of how ___________ a device does work.

Power is equal to work done in _________divided by thetime taken.

The _________ of a device is also equal to the rate at which adevice transforms ___________ from one form to another.

Power is measured in _________, symbol W.

A one kilowatt motor will perform one ____________ joulesof work every __________.

joules energy

thousandquickly power

watts

second

WORD SELECTION:

joules

energy

thousand

quickly

power

watts

second


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Online SimulationsWork (GCSE) - Powerpoint presentation by KTKinetic Energy (GCSE) - Powerpoint presentation by KT

Gravitational Potential Energy (GCSE) - Powerpoint presentation by KTBouncing ball with different surfaces showing KE & PE - Freezeway.comEnergy Skate Park - Colorado - Learn about conservation of energy with a skater dude!Build tracks, ramps and jumps for the skater and view the kinetic energy, potentialenergy and friction as he moves. You can also take the skater to different planets oreven space!Rollercoaster Demo - Funderstanding

Energy conservation with falling particles - NTNUBall rolling up a slope - NTNUPulley System - FendtBicycle gear distance multiplier demonstration - Freezeway.comBBC AQA GCSE Bitesize Revision:Work, force and distance Potential and kinetic energy Kinetic energy equation
http://www.ktaggart.co.uk/physics/PowerPoint/Work.ppthttp://www.ktaggart.co.uk/physics/PowerPoint/KineticEnergy.ppthttp://www.ktaggart.co.uk/physics/PowerPoint/GPEnergy.ppthttp://www.freezeray.com/flashFiles/bouncingBall.htmhttp://phet.colorado.edu/new/simulations/sims.php?sim=Energy_Skate_Parkhttp://www.funderstanding.com/k12/coaster/http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=197.0http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=422.0http://www.walter-fendt.de/ph14e/pulleysystem.htmhttp://www.freezeray.com/flashFiles/distanceMultiplier1.htmhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/kineticenergyrev1.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/kineticenergyrev2.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/kineticenergyrev5.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/kineticenergyrev5.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/kineticenergyrev2.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/kineticenergyrev1.shtmlhttp://www.freezeray.com/flashFiles/distanceMultiplier1.htmhttp://www.walter-fendt.de/ph14e/pulleysystem.htmhttp://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=422.0http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=197.0http://www.funderstanding.com/k12/coaster/http://phet.colorado.edu/new/simulations/sims.php?sim=Energy_Skate_Parkhttp://www.freezeray.com/flashFiles/bouncingBall.htmhttp://www.ktaggart.co.uk/physics/PowerPoint/GPEnergy.ppthttp://www.ktaggart.co.uk/physics/PowerPoint/KineticEnergy.ppthttp://www.ktaggart.co.uk/physics/PowerPoint/Work.ppt


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EDEXCEL IGCSE / CERTIFICATE IN PHYSICS 4-1

Energy TransfersEdexcel IGCSE Physics pages 127 to 132

June 17 th 2012

All content applies for Triple & Double Science


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Edexcel Specification

Section 4: Energy resources and energy transfer b) Energy transferdescribe energy transfers involving the following forms of energy:thermal (heat), light, electrical, sound, kinetic, chemical, nuclear andpotential (elastic and gravitational)understand that energy is conservedknow and use the relationship:efficiency = useful energy output / total energy inputdescribe a variety of everyday and scientific devices and situations,explaining the fate of the input energy in terms of the aboverelationship, including their representation by Sankey diagrams


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Forms of energy

1. THERMALor HEAT ENERGYThis is the energy of an

object due to itstemperature.

2. LIGHT ENERGY

This is energy in the formof visible electromagneticradiation.

Energy can exist in many forms.


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3. ELECTRICAL ENERGYThis is the energy

transferred by an electriccurrent.

4. SOUND ENERGYThis is energy in the formof a sound wave.


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5. KINETIC ENERGYThis is the energypossessed by a movingobject.

Kinetic energy increases is

the objects speed isincreased.

Also often calledMovement energy


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6. CHEMICAL ENERGYThis is energy that is releasedwhen chemical reactions take

place.

Sources of chemical energyinclude:fuel, food and batteries.

7. NUCLEAR ENERGYThis is energy that is releasedwhen nuclear reactions takeplace.This is the source of theSuns energy.
http://images.google.com/imgres?imgurl=http://xprizecars.com/images/Battery_9V.jpg&imgrefurl=http://xprizecars.com/2008/04/batteries-power-energy-and-uni.php&usg=__yb0uGZZ87hS6Vp2aTqCxWWWaYBU=&h=300&w=300&sz=9&hl=en&start=1&itbs=1&tbnid=EtUZ-5HXzfpWAM:&tbnh=116&tbnw=116&prev=/images%3Fq%3Dbattery%26hl%3Den%26gbv%3D2%26tbs%3Disch:1


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8. POTENTIAL ENERGYThis is the energy possessed anobject due to its position.

Gravitational Potential EnergyThe gravitational potential energy ofan object increases if it is raisedupwards.

Elastic Potential Energy

Gravitational potentialenergy being convertedinto kinetic energy.

This is the energystored in a stretched

or squashed object- also known as strainenergy


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Other energy measurement examples

4200 joules (4.2 kJ) 1 food Calorie

1 000 000 J (1 MJ) Energy of a Mars bar

0.000 02 J Energy need to produce asyllable of a word

15 000 000 000 000000 000 000 J

Energy received by the Earthfrom the Sun in one day


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Conservation of energy

Energy cannot be created or destroyed. Itcan only be transformed from one formto another form.

Conservation of energy also means that thetotal energy in the universe stays constant.


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Pendulum oscillation

GRAVITATIOINAL POTENTIAL ENERGY

KINETIC ENERGY

MAXIMUM

MINIMUMMAXIMUM

ZERO

The total energy, gravitational

potential plus kinetic, remainsthe same if there are nosignificant resistive forces


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Useful and wasted energyUseful energy is energy transferred to where it is

required in the form that it is wanted.

Other forms of energy are referred to as wasted .

Wasted energy spreads out into the surroundings.

This is usually in the form of heat energy causingthe energy changing device and its surroundings to

become warmer. It is very difficult to concentratethis energy again to make use of it.


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Energy efficient light bulbs

These produce more usefullight energy for the sameamount of input electrical

energy. They waste less energy toheat.
http://images.google.co.uk/imgres?imgurl=http://www.miss-thrifty.co.uk/wp-content/uploads/2008/08/energy-saving-light-bulb.bmp&imgrefurl=http://www.miss-thrifty.co.uk/2008/08/08/friday-bargain-energy-saving-lightbulbs-for-next-to-nothing/&usg=__WC2XbULS0K6f3LmLtwJBymMFfl4=&h=520&w=567&sz=866&hl=en&start=30&um=1&itbs=1&tbnid=kQodO86Xf6w8CM:&tbnh=123&tbnw=134&prev=/images%3Fq%3Denergy%2Befficient%2Blight%2Bbulb%26start%3D18%26um%3D1%26hl%3Den%26sa%3DN%26ndsp%3D18%26tbs%3Disch:1http://images.google.co.uk/imgres?imgurl=http://mypumpkindoodle.com/store/images/pa15_250.jpg&imgrefurl=http://mypumpkindoodle.com/store/pureairhomeproductspurelyanion-c-179_104_105.html&usg=__IoxKvCb3Nczma3d-kb7pGenlo98=&h=250&w=250&sz=9&hl=en&start=28&um=1&itbs=1&tbnid=vdJi-6azDiJ2uM:&tbnh=111&tbnw=111&prev=/images%3Fq%3Denergy%2Befficient%2Blight%2Bbulb%26start%3D18%26um%3D1%26hl%3Den%26sa%3DN%26ndsp%3D18%26tbs%3Disch:1


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Question 1Calculate the efficiency of an electric motor if it

produces 48J of useful kinetic energy whensupplied with 80J of electrical energy.

efficiency =useful energy output

total energy input

efficiency = 48J 80J

efficiency of the motor = 0.6


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Question 2Calculate the useful light output of a light bulb ofefficiency 0.20 when it is of an electric motor if itsupplied with 400J of electrical energy.

0.20 = useful energy 400J

useful energy = 0.20 x 400J

light output = 80J

efficiency =useful energy output

total energy input


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Percentage efficiency

percentage efficiency = efficiency x 100

The greater the percentage of the energy

that is usefully transformed in a device, themore efficient the device is.

The maximum percentage efficiency is 100%


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CompleteInput

energy (J)

Useful

energy (J)

Wasted

energy (J)

Efficiency Percentage

efficiency

100 40

250 50

50 0.20

80 30%

60 60

60

200

10 40

24 56

120

0.80

0.50

0.30

20%

0.40

80%

50%

40%

Answers


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Improving efficiency

Decrease loss to heat by:Reducing friction by using a lubricant (eg oil).Reducing electrical resistance in electrical

circuits.Reducing air resistance by using streamlined

shapes.

Reduce loss to sound by tightening theloose parts of machinery.


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Energy flow diagrams

GENERAL DIAGRAM

DEVICECAUSINGENERGYCHANGE

INPUTENERGY

WASTEDENERGY

USEFULOUTPUTENERGY


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An electric light bulb

lightbulb

electricalenergy

heatenergy

lightenergy
http://images.google.com/imgres?imgurl=http://www.physics.uiowa.edu/adventure/fall_2005/oct_15-05/light_bulb.jpg&imgrefurl=http://www.physics.uiowa.edu/adventure/fall_2005/oct_15-05.html&usg=__UgqSve7q4DLlpI2DotZyLA8HOX0=&h=504&w=292&sz=19&hl=en&start=7&itbs=1&tbnid=ZSMaKMmWo9wUQM:&tbnh=130&tbnw=75&prev=/images%3Fq%3Dlight%2Bbulb%26hl%3Den%26sa%3DG%26gbv%3D2%26tbs%3Disch:1


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Microphone

microphone

soundenergy

heatenergy

electricalenergy


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Car engine

carengine

chemicalenergy

heat &soundenergy

kineticenergy
http://images.google.com/imgres?imgurl=http://www.toponlinequotes.co.uk/images/car%2520cartoon%25203%2520logo.jpg&imgrefurl=http://myvintagekitschen.com/2007/09/&usg=__f1BWEKnYdXewP9WYNSt5yVQn0CI=&h=328&w=482&sz=28&hl=en&start=1&itbs=1&tbnid=YNKxzqUybb0YkM:&tbnh=88&tbnw=129&prev=/images%3Fq%3Dfast%2Bcar%2Bcartoon%26hl%3Den%26sa%3DX%26gbv%3D2%26ndsp%3D18%26tbs%3Disch:1


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C l h bl b l


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Complete the table below:Device Input energy Main output

energyElectric motor electrical

Car brakes heat

gravitationalpotential

kinetic

Candle light

Generator electrical

kinetic

kinetic

chemical

kinetic

Falling object

Sankey Diagrams


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Sankey DiagramsThese are energy flowdiagrams that show howwell a device usesenergy.

The width of the flowarrows is proportional tothe amount of energy

Wasted energy is shownflowing downwards.

DeviceINPUTUSEFULOUTPUT

WASTED

OUTPUT

Question


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QuestionDraw a Sankey diagram for car of efficiency 20%

CARCHEMICALENERGY

KINETICENERGY

HEAT &SOUND

ENERGY

The kinetic energy arrow should be 1/5 th the width of the chemical energy arrow.

The heat & sound arrow should be 4/5 th the width of the chemical energy arrow.



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Energy is required to do ________.

Energy is measured in ________ (J)Energy cannot be created or ___________ but can onlychange ________.

Kinetic energy is the energy possessed by __________ bodies.

When an object is lifted up it gains gravitational _____________ energy.

Heat or __________ energy is often produced as a _________

energy form.

workform

moving joulespotential thermal destroyedWORD SELECTION:

wasted

work

form

moving

joules

potential

thermal

destroyed

wasted

O li Si l ti


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Online SimulationsEnergy Conservation - 'Whys Guy' Video Clip (4:40 mins) - IncludesBowling Ball Pendulum DemonstrationSequential Puzzle on Energy Size - by KT - Microsoft WORDHidden Pairs Game on Energy Transfers - by KT - Microsoft WORDEnergy conversions & efficiency calculations - eChalkEnergy transfer bounce quizes - eChalkBBC AQA GCSE Bitesize Revision:Forms of energy Energy transfer - includes Sankey diagramEfficiency - includes Sankey diagramsBBC KS3 Bitesize Revision:

Energy basics - Forms of energyEnergy transfer diagrams - includes Sankey diagram

Energy Transfers
http://web.hep.uiuc.edu/home/MATS/WCIA/wcia_030122_2.wmvhttp://www.ktaggart.co.uk/physics/Games/SequenceEnergySize.dochttp://www.ktaggart.co.uk/physics/Games/PairsEnergyTransfers.dochttp://subscription.echalk.co.uk/index.htmhttp://subscription.echalk.co.uk/index.htmhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/energy/heatrev4.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/energy/heatrev4.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/energy/heatrev6.shtmlhttp://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/energy_transfer_storage/revise2.shtmlhttp://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/energy_transfer_storage/revise3.shtmlhttp://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/energy_transfer_storage/revise3.shtmlhttp://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/energy_transfer_storage/revise2.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/energy/heatrev6.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/energy/heatrev4.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/energy/heatrev4.shtmlhttp://subscription.echalk.co.uk/index.htmhttp://subscription.echalk.co.uk/index.htmhttp://www.ktaggart.co.uk/physics/Games/PairsEnergyTransfers.dochttp://www.ktaggart.co.uk/physics/Games/SequenceEnergySize.dochttp://web.hep.uiuc.edu/home/MATS/WCIA/wcia_030122_2.wmv


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Energy TransfersNotes questions from pages 127 to 132

1. (a) What is energy? (b) State the unit of energy. (see page 127)2. Give examples of the following energy changes: (a) electrical to

light; (b) kinetic to sound; (c) nuclear to light; (d) chemical togravitational potential; (e) elastic potential to thermal. (see pages128 and 129)

3. State the law of conservation of energy and give an example (seepages 129 and 130)

4. Sketch a Sankey diagram showing the energy flow in an electriclight bulb. (see pages 130 and 131)

5. Define (a) efficiency; (b) percentage efficiency. Calculate both ofthese for an electric motor that uses 120J of electrical energy tooutput 90J of kinetic energy. (see page 131)

6. Answer the questions on page 132.7. Verify that you can do all of the items listed in the end of chapter

checklist on page 132.

Yr 9 Work Power Energy Revision

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