Forces Basic

8/13/2019 Forces Basic

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e"f- #estUnit $ Pushes and Pu""sUnit % Forces Act in Particu"ar DirectionsUnit & 'a"anced ForcesUnit Frictiona" Forces

!nternet ites'i"io*raphyEva"uation of this pre-course pack+

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!ntroduction#his pack is desi*ned for primary PGCE trainees ,ho need to improve

persona" ack*round kno,"ed*e of science+ !mproved science kno,"ed*e,i"" mean that you can e more confident and effective ,hen teachin*

science throu*hout the primary years+ o matter ,hat a*e ran*e youintend to teach there are minimum re.uirements for ack*roundkno,"ed*e ,hich are rou*h"y e.uiva"ent to *ood GCE pass+ P"ease ereassured/ primary trainees in the past have 0oined the course fee"in* veryapprehensive aout science ut yet a"" make very si*nificant pro*ress+#his is part"y ecause of the carefu" structure of the course/ the .ua"ity ofthe support avai"a"e and a"so the fact that there is nothin* .uite "iketeachin* a topic to he"p c"arify it in your mind1

(#his pack is in draft format and ,i"" e added to/ your feedack at thissta*e ,i"" e very usefu"+)

2hy Forces3#his has een se"ected as it is an area many adu"ts and chi"dren findcha""en*in* and ,here improved understandin* can e achieved throu*hstrai*htfor,ard activities+

2i"" this Pack 4e"p 5ou3#ry the .uestions in the pre-pack se"f test/ if you *ive ans,ers ,hich are

simi"ar to those *iven and you understand these concepts/ you proa"ydon6t need this pack+ 4o,ever even if your science is stron* this pack,i"" e of interest as a e7amp"e of the sort of materia"s non-specia"istco""ea*ues mi*ht re.uire+ 8ther,ise read throu*h the materia"s/ try thesimp"e activities and take up some ack*round readin*+ !n any case youshou"d keep this pack/ inc"udin* the se"f-test/ as the resu"ts provideevidence of your kno,"ed*e in science+ 2hi"st on the course you ,i""need such evidence of "earnin* for your science independent "earnin* fi"e+

2hat E.uipment 2i"" ! 9e.uire3


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a heavy book

string

an elastic band

a pair of scissors

2 pairs of footwear a tray

4o, Much #ime is 9e.uired3#his is hard to ans,er/ some peop"e may need &: minutes for each unit/others dou"e this/ it rather depends on your present understandin* andho, you react to the materia"s+

8ne thin* ,hich you ,i"" "earn on the tau*ht course is that ,e a"" have

our o,n ideas and e7p"anations for ,hy thin*s happen in the ,or"d+ometimes it can take "on*er than you ,ou"d think to adapt or chan*esuch ideas+ Don6t e upset if these concepts seem difficu"t+

2hy have ! een sent this pack3As you may kno, the primary PGCE course has a",ays eencha""en*in*+ 9ecent *overnment stipu"ations mean that to pass the courseyou ,i"" have to achieve certain ;standards6 of su0ect kno,"ed*e inscience/ En*"ish and mathematics+ #his pack is intended to reduce your,ork"oad in the comin* year (see the i"io*raphy for su**ested te7ts,hich ,ou"d assist you further)+

Aim of the Pack#he aim of this pack is to assist those ,ho have never or not recent"ystudied this area of science+ !t shou"d *ive you e7perience e7p"orin* anarea (practica""y and ,ith your .uestions) and mi*ht assist you inc"arifyin* your thou*hts+ Don6t e suprised if you come a,ay from the

pack ,ith more .uestions than ,hen you started+ !f this is the case thepack has assisted+ ome further ack*round readin* ,i"" assist you+

Pre-Pack e"f-#est


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2herever a force is app"ied it appears as a push or a pu""+ #hese forces can e "ar*e"ike the force of the u""do=ers aove or very sma"" "ike the pu""in* force you ,i"" useto turn this pa*e+ 8ne pro"em for us as science teachers is that humans are rare"y

a,are of these sma"" forces+ #his can make "earnin* aout forces a "itt"e harder+

Can you "ist thin*s that you push and pu"" around your home3

thin*s ! push thin*s ! pu""

o, oserve the action of a pair of scissors+ Pick them up and use them in a cuttin*action+ Can you fee" that you are pushin* and pu""in*3 Can you fee" your fin*ers andthum pushin* the scissors c"osed3 Can you fee" that your fin*ers and thum have to

pu"" them apart3 A pair of scissors is a very simp"e machine ,hich takes your pushin*and pu""in* of the hand"es and transfers the movement to the "ades ,here the "ades

are pushed to*ether so c"ose"y and firm"y that ,hen in contact ,ith paper or card themateria" is cut+ 2hat happens to the pushin* force ,hen you try to cut thicker card3Summary of Unit 1We experiences forces as pushes and pulls.Forces can vary in magnitude.

any small pushes and pulls go unnoticed by humans.notes>.uestions

Unit 2 - Forces Act in Particular irections

#hrou*hout your "ife you have e7perienced forces+ #hese inc"ude the force of *ravity

,hich is present"y pu""in* you and the o0ects around you to,ards the centre of theEarth+ 8ther fami"iar forces inc"ude the force you fee" on the seate"t ,hen you are in acar ,hich is s"o,in* do,n and the force on your ody as you *et pushed in a cro,d+

Each of these forces is pushin* or pu""in* in a particu"ar direction and ,i"" resu"t insomethin* speeding up/ slowing down! c"anging direction! #aintaining aconstant speedor a state of rest+ #he "ast sentence is a mouthfu"1 P"ease read it a*ainand think ,hat it means y speedin* up/ s"o,in*/ do,n/ constant speed and state ofrest+

#hou*ht E7periment!f a "ar*e ho"e appeared in the f"oor e"o, your chair ,here ,ou"d you


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and the chair *o3

!f your response inc"udes a 0ourney a"on* a strai*ht "ine to,ardsthe centre of the Earth/ you have *ot the idea1

#hou*ht E7perimentAs a tennis p"ayer hits a tennis a"" ,ith the racket a force is app"ied ,hich sends the

a"" throu*h the air+

Can you think of thin*s ,hich the a"" mi*ht encounter on its path ,hich ,ou"d chan*eits direction3

the net3a ,a""3

the racket of the other p"ayer3the air3*ravity3

2e ,ou"d have no difficu"ty a*reein* that the first three ,ou"d affect the 0ourney ofthe a""+ Each ,ou"d app"y a ne, force in a different direction affectin* the 0ourney ofthe a""+ 2e cou"d discuss the "ast one ,hich ,i"" affect the f"i*ht of the a"" ut to asma"" e7tent+ 5ou can ima*ine tennis p"ayers comp"ainin* aout stron* (or even "i*ht)cross ,inds1 #hey ,ou"d e un"ike"y to comp"ain aout *ravity ut ,i"" e very ski""edat accountin* for its effects+ Do you a*ree ,ith the idea of a *ust of ,ind app"yin* aforce3 (!f this is difficu"t/ think of a sai"in* ship+ 2hat is it that pushes the sai"in* shipfor,ard3) !n a *ame of tennis each p"ayer see to a"ter the direction and speed of the

a"" in such a ,ay as to make a successfu" return impossi"e+

4o, many other *ames are p"ayed ,here the p"ayers chan*e the direction and speed

of a a""/ or puck3

Forces a",ays act in a strai*ht "ine+ 8ur pro"em on Earth is that ecause of *ravitya""s and other o0ects ,hich start their 0ourney in a strai*ht "ine are immediate"yinf"uenced y *ravity as the o0ect is pu""ed to,ards the centre of the Earth+

!f/ for e7amp"e/ a foota""er ,ishes to make a "on* pass to a p"ayer in the *oa"mouth+he or he must app"y a force ,hich ,i"" initia""y send the a"" on a strai*ht "ine path,hich ,ou"d *o far too hi*h+ As the a"" trave"s *ravity ,i"" pu"" the a"" a"on* a curved

path+ #his means that on"y a very ,e"" 0ud*ed kick ,i"" "and at the feet of the otherp"ayer1


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#he dotted "ine sho,s the initia""ine of trave"+ #his is

affected y *ravity+

As ,e said aove/ the force of *ravity ,i"" pu"" the a"" do,n to,ards the centre of theEarth+ Another force ,i"" affect the a"" in its f"i*ht+ As the a"" has to trave" throu*hair/ the air has a s"i*ht ut si*nificant s"o,in* affect on the a""+ #his is the force of airresistance+ Can you think of other instances ,here air resistance interferes ,ith>assists human activities3 i+e+ s"o,in* a car/ a p"ane/ a train/ turnin* the sai"s of a,indmi""+

Summary of Unit 2We experience forces as pushes or pulls.

Forces make things speed up! slow down! change direction! remain at a constantspeed or state of rest.Forces always act in a straight line."ravity affects the movement of ob#ects.

$ir resistance slows things down.

notes>.uestions

Unit 3 $alanced and Un%alanced Forces8ur e7perience of forces is that they act in pairs+ As your ody is attracted to,ardsthe centre of the Earth this is matched y an e.ua" and opposite force from the chairon ,hich you are sittin*+ #hus you are at rest/ the opposin* forces are a"anced+ 2henthe forces produce a state of rest "ike this or #ove#ent at a constant speed theforces are %alanced+ ?ots of other e7amp"es e7ist as ,e are surrounded y them in ourdai"y "ives+

$) 2hen you see a *ymnast standin* on a trampo"ine you can ;see6 that theforce of *ravity is pu""in* the *ymnast do,n and that the faric ande"astic of the trampo"ine is reactin* ,ith an e.ua" force pushin* in theopposite direction+

%) 2hen opposin* teams in a tu*-o-,ar pu"" in opposite directions one canappreciate that for short periods the forces are in a"ance+ (2hi"st othteams are pu""in* ,ith e.ua" force there is no movement re"ative to the f"oor+)

&) A parachutist in free fa"" ,i"" reach termina" ve"ocity ($%:mph)+ At this pointthere is no acce"eration or dece"eration so ,e have movement at constant speed

,ith a"ance et,een the do,n,ard pu""in* force of *ravity and the up,ardpushin* force of air resistance+


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Forces act in pairs and are either a"anced (the o0ect is at rest or movin* at a steadyspeed) or una"anced (the o0ect is acce"eratin* or dece"eratin*)+2e often havedifficu"ty dea"in* ,ith forces in primary c"assrooms ecause every i""ustration ,e *ive,i"" e affected y *ravity and frictiona" forces "ike air resistance+

Put your hands to*ether ,ithout pressin*/ can you no, press ,ith one hand anda"ance this ,ith the other so that the hands do not move3 #ry it3

5ou ,ere successfu" even if there ,as a "itt"e movement ecause you shou"d have ;fe"tthe force6+ ?ike chi"dren ,e a"" "earn these concepts etter if ,e can ;fee"6 the force+

#hou*ht E7perimento, consider the different sta*es in a *ame of *o"f and the effect of forces on the *o"fa""+ !nitia""y the *o"f a"" is at rest on the tee+ #he forces actin* on the a"" are +++

#he forces actin* on the stationary a"" are those of *ravity and the opposite force ofthe tee+ #hese forces are a"anced/ the a"" is at rest+

As the c"u hits the a"" a ne, side,ays force is app"ied+

For the ne7t second or t,o the a"" acce"erates (forces are una"anced) a,ay from thep"ayer a"on* the fair,ay+ 2ithin a fe, seconds the forces of *ravity and of airresistance retard the movement of the a"" ,hich dece"erates (una"anced forces)eventua""y it comes to a stop on the *reen (the forces are a"anced a*ain)+

E7perimento, tie your strin* around the ook and onto the e"astic and as in the dia*rame"o,+ #his may take a moment ut ,i"" e very usefu"+

'efore you pu"" on the e"astic/ make a prediction/ ho, hard ,i"" you have to pu""efore the ook moves3 tart pu""in* ,ith a very *ent"e force so that the ook does

not move (forces are a"anced)+


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As you pu"" can you see the e"astic and stretch3 As it stretches it is *ivin* you anindication of the force you are e7ertin* on the ook+ 8nce a certain point is reachedthe ook moves+

Gent"y increase the pu""in* force unti" the ook moves+ For a sp"it second (you ,i"" not

notice) the ook acce"erates (una"anced forces)+ @eep the pu""in* force the same andthe speed of the ook ,i"" remain constant (a"anced forces)+

2hy does the ook not move ,ith the initia" "i*ht pu""in* force3

!nitia""y the ook remains sti"" ecause the friction et,een the ook and the ta"e topis considera"e and so the ook and ta"e top app"y an e.ua" resistive force to your pu""(a"anced forces)+

ook does not move

*ent"e pu""

frictiona" forces

2hat is it aout the *reater ma*nitude of force ,hich makes the ook move3

As you s"o,"y increase the force/ a point is reached ,here the resistive force caused ythe friction et,een the ook and ta"e top is overcome+ As you pu"" the ook acrossthe ta"e at a constant speed no further increase in pu""in* force is re.uired+ !f you

maintained this pu""in* force on a very "on* ta"e the ook ,ou"d *o on and on1 #hus,e ,ou"d have an o0ect movin* at a steady speed ,ith a"anced forces+

ook moves

i**er pu""

frictiona" forces

!f you app"y a further increase to the pu""in* force/ the speed of the ook ,i"" increase(una"anced forces - acce"eration)+ #hus ,e ,ou"d have una"anced forces producin*acce"eration+

#ry repeatin* the e7periment and considerin* the forces at each sta*e+ #ry pu""in*other o0ects or the same ook on a different surface+ Predict ,hat ,i"" happen+

!t may assist you to repeat this ,ith a friend (not pu""in* them ,ith an e"astic and1)+Make the oservations to*ether and ta"k it over+

Summary of Unit %

Forces act in pairs. &hey usually oppose one another and when balanced areconsidered e'ual and opposite.


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Forces are balanced when an ob#ect is stationary (at rest) or when the ob#ect ismoving at a constant speed.

$cceleration and deceleration only occur when the forces are out of balance.

notes>.uestions

Unit Frictiona" Forces

2e have a"ready considered e7amp"es of friction+ Friction et,een a ook and a ta"etop and et,een a a"" and the air (air resistance)+

Friction is a"" around us/ it can e oth our enemy and our friend+ Friction costs youmoney as the en*ine of your vehic"e ,orks hard to overcome friction+ Friction savesyour "ife ,hen the rakes of a vehic"e rin* it safe"y to rest1

#hink aout the different foot,ear ,hich you use+ Are some pieces of foot,ear ettersuited for use in ,et or icy conditions3 !n ,et or icy conditions you ,ant shoes ,ith a*ood *rip+ 'y this ,e mi*ht mean a pattern cut into the so"e to *ive etter *rip(increased friction)/ or ,e mi*ht mean the materia" from ,hich the so"e is made/ assome materia"s *ive etter *rip (produce more friction)+

A simp"e e7periment ,ou"d see you p"acin* different items of foot,ear on a tray or

other f"at surface and carefu""y tippin* the tray+ #he shoes ,ith more *rip (*reaterfrictiona" forces) ,i"" e the "ast to move (take care not to cause any dama*e1)+

#ry this ,ith different shoes+ #ry to predict ,hich ,i"" e the est+

At the end of this e7periment can you descrie the characteristics of materia"s ,hichprovide *ood *rip3 !s it ruery3 soft3 *rippy3 endy3 smooth3 rou*h3 ++++++++++++++++3

e7t time you *o to uy a pair of shoes you mi*ht refer to your need for increasedfrictiona" forces rather than *rip1


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!n unit t,o ,e considered the force of air resistance+ hips/ oats/ sumarines and fisha"" have to contend ,ith the simi"ar effects of ,ater resistance+ 4o, do fish reduce thefrictiona" forces on their odies as they move throu*h ,ater3

stream"ined shapes"ippery surfacefe, protrusions

4o, does a sumarine copy these characteristics3

2e humans do the est ,e can ,ith our sumarines/ ships and oats choosin* shapesthat ,i"" *"ide throu*h the ,ater and materia"s ,hich are as smooth as ,e caneconomica""y make them+

Friction he"ps us to ,a"k+ 4ave you ever tried to ,a"k on ice3 #ry ,a"kin* around theroom you are in+ !f you ,a"k s"o,"y and concentrate hard you may e a"e to fee" eachfoot as it pushes do,n and s"i*ht"y ack,ards ,ith each step+ 2ithout this frictiona""o,in* you to push ack a*ainst the f"oor you ,ou"d *et no,here+

4o, do 8"ympic s,immers reduce the frictiona" forces of ,ater resistance3

smooth s,imsuitsa"d heads

s,immin* capsremova" for ody hair1

4o, do aerop"ane manufacturers reduce the frictiona" forces of air resistance in theirp"anes3

smooth materia"saerodynamic shape

fe, protrusions


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#hou*ht E7perimentAs a driver attempts to drive a,ay from a muddy fie"d the ,hee"s of the car spinon the mud+ 2hat ,i"" the affect of this e on her ai"ity to make pro*ress3

'ecause there is insufficient friction et,een the tyres and the *round+ #he mud isactin* as a "uricant (rather "ike oi") and is reducin* the friction+ 8n"y if the frictiona"forces can e increased ,i"" the car move+ More frictiona" forces mi*ht e achieved ifthe driver ,ere to put sand or stones eneath the ,hee" to reduce the "uricatin* effect

of the mud+ #hus the ,hee" cou"d ;*et a *rip6 (e7perience sufficient friction)+

Summary of Unit *

Frictional forces are all around us.

Frictional forces both assist us and hinder us.+umankind often adapts products to either increase or decrease frictional forces.+umankind often copies the natural world in order to decrease frictional forces+

notes>.uestions

!nternet ites for cience

&ry these ,nternet sites if you have access! what do they tell you about science and about primaryscience-

comments

http//www.sodaplay.com

http//think'uestorg/20/

http//www.pcet.co.uk/primary/pscience/t1%*.htm

http//www.darvill.clara.net/enforcemot/forces.htm

http//www.ase.org.uk


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http//www.sciencenet.org.uk

http//www.bbc.co.uk/education/revisewise/science/physical/index.shtml

try our 3"45 3rimary site and go to science and science links

http//www.education6man.ac.uk/pgce/primary

other sites you find

Further 7eading 8ethell! ". (1990) :xford 7evision "uides Science &hrough ;iagrams! :xford :xford

University 3ress. ,S8< =>19>91*0=?>@ Farrow! S. (199?) &he 7eally Useful Science 8ook! Falmer 3ress Aondon. ,S8< = 0=0 =%0?

Bent! $. and Ward! $. (19*) &he Usbourne 8ook of 3hysics! Aondon Usborne 3ublishing. ,S8< = 0*?= =%= 9 3eacock! ". (199) C&S Science for 3rimary &eachers $n $udit and Self>Study "uide! Aondon

Aetts 5ducational. ,S8< 1>=>%=>1

Eva"uation - Forces - Precourse tudy Pack Primary PGCEP"ease score the fo""o,in* on the $ - & sca"e and ,here you ,ish add a comment+

*ood satisfactory poorthe presentation of units $ % &

*ood satisfactory poorthe content $ % &

the or*anisation *ood satisfactory poor$ % &

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P"ease add any other comments aout this pack ,hich ,ou"d assist trainees in the future+


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P"ease note any usefu" ,esites you have discovered+

P"ease post this to A"an Cross/ Department of Education/ University of Manchester/ 87ford 9oad/Manchester/ M$& P?+ or *ive it to him in the first ,eek of the course+ Comments can a"so e *ivenon a"an+crossBman+ac+uk

Forces Basic

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