VerticallyChallenged - flying cornflakes

8/7/2019 VerticallyChallenged - flying cornflakes

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VerticallyChallenged

Part of the British Science AssociationsNational Science & Engineering WeekActivity Pack Series.

For further information visitwww.nsew.org.uk

National Science & Engineering Week isfunded by the Department forBusiness, Innovation and Skills


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Download more a c tivity pa c ks for Nationa l Scienc e & Engineering Wee k at www.nsew.org.uk 1

About this Pac k

BackgroundThis ac tivity pa c k is c onc erned with b uild ings and the forc es tha t a re req uired to put them

together. The a c tivities inc luded in this pac k will show how build ings a re c onstruc ted usingsc ientific ide as. Whether it is a to we r ma de out o f spaghe tti, a b ridge ma de out o f pa per or

glue made o ut of m ilk; you will be a b le to investiga te w ha t it ta kes to m ake a real life eng inee r

or architect!

The first sec tion c onta ins deta ils on how to c a rry out the ac tivities. The sec ond sec tion ha s

background note s on the sc ienc e b ehind the a c tivities.

Sc ienc e safetySom e o f these a c tivities involve using pote ntially da ngerous ob jec ts. Please read ea c h ac tivity

ca refully, and ta ke ap p rop riate m ea sures to e nsure the sa fety and enjoyment of a ll

participants.

Educ ationa l LinksAll ac tivities in this pac k contribute toward s Key Sta ge 1 Inve stiga tion and Skills in sc ienc e, Skills

in designing a nd ma king and Skills in soc ial sub jec ts in the 5-14 Guidelines. We rec om mend tha t

you c onsult the Nationa l Curriculum on the web site (www.nc.uk.net/), and the 5-14 Guide lines

(www.ltscotland.org.uk/5to14).

AcknowledgementsThe a c tivities in this pac k we re c om p iled and a dapted from a num ber of sources. Ma ny thanks

go to a ll to w ho he lped in the m aking o f this pac k, in pa rticula r, Elizabeth Rob ertson w ho

dona ted Ac tivity 13 from her bo ok The Insta nt Egg Rac e File - a c ollec tion of t ried and tested

p rac tica l p rob lem-solving ac tivities . To obta in a c op y of this pub lica tion send 7.50 (which

includes posta ge and pac king ) to Sc ienc e Designs, 6G Sa lmon Lane, Stonehaven AB39 2NZ.

For more informa tion on projects, resources and events which eng ag e young peo p le in their

built environm ent a nd the space a round them , c hec k out the C ABE Educa tion web site a t

www.cabe-education.org.uk/


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Activities

Ac tivity 1:A question of ba lance

You will need :A long stick e.g. a wa lking stick or a ruler, a p iece o f c lay or a w eight , sticky tape

First, plac e yo ur fingers a t eac h end of the stick and mo ve them inwards until the stick is

ba lanc ed . This is the c entre of gravity. Next a tta c h a piec e o f clay, or we ight , onto the stic k

with tap e. Try ba lanc ing the stic k on your finge rs now . Has the c entre of gravity change d?

Rep ea t the experime nt b y cha nging the position a nd size o f the w eight. Where do you think the

c entre of gravity would b e in different objec ts, for examp le, a d oug hnut, your bod y, your

house, the Earth?

Ac tivity 2:Whats long and sticky ?

You will need :A long thin stick (ab out 1 me tre), a p iece o f clay or Plasticine

Atta c h a p iece o f c lay, about the size o f your fist, ab out 20 cm from the e nd of your stick. Try to

ba lanc e the stic k vertica lly on the e nd of your finge r; first b alanc ing w ith the c lay at the botto m

of the stic k and then w ith it a t the to p . Whic h is ea siest? How long c an you b a lanc e the stic k

for?

Ac tivity 3:Lift up a grown up

You will need :An adult, a c hild , a long plank of wo od , a b loc k of som e sort (wo od or a b ric k)

First, ma ke your leve r by plac ing the p lank

of woo d on top o f your bloc k. Your leve r

will work be st if the b loc k is c loser to one

end so tha t the lever is unba lanc ed .

Next, get your ad ult volunteer to sta nd on

the short end of t he lever whilst the c hild

sta nd s on the long end . Ca n the c hild lift the adult? How is this possible?

Ac tivity 4:Flying cornflakes!

You will need :An ice lolly stick, a penc il, c erea l, a me tre ruler, a small c onta iner

Put the ice lolly stick, a t right a ng les, ac ross the p enc il. Put a p iece of c erea l on one end of the

stick, hit the othe r end of the stic k with your hand and wa tc h out for flying c ornflakes!

If you ma rk where the p enc il is and rec ord the d istanc e tha t the c ereal flew , you should no w b e


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ab le to plac e a sma ll conta iner at this distanc e a nd try ag ain to see if ca n c atc h your c erea l.

Ac tivity 5:Stac k A ttac k

You will need : 15 20 rec ta ngular, fla t b loc ks of the same size a nd shape (fo r exam ple, youc ould use textboo ks, playing c a rds, wood en b locks, or fla t rulers)

Sta ck the b loc ks, one o n top o f anothe r, to ma ke a co lumn. Sta rt by moving the top b loc k as

far to the right as possible without it falling off the sta c k. Next, mo ve the top two b loc ks

together so tha t they both extend ove r the third b lock as fa r as possible without fa lling off. Now

mo ve the top three b loc ks, and then the top four b loc ks and so on d ow n the stac k. How m any

bloc ks do you have to move be fore the to p b loc k is c omp letely be yond the b ase of the stac k?

Ac tivity 6:Do less work!

You will need :Strong string (about a met re), sc issors, a b oo k, a rolling p in

Tie a long p iece o f string sec urely around your bo ok ma king sure there is eno ugh left to run over

your rolling p in. Plac e the boo k on the floo r and lift it by pulling on the string. Think about how

muc h forc e is req uired to p ick it up . Now g et som eo ne to hold the rolling p in loo sely by the

ha nd les. Run the string over the top o f the rolling p in and p ull dow n on it to lift the bo ok. How

muc h force w as req uired this time? Is it easier or harde r?

The rolling p in is ac ting as a pulley . What d o you think would ha ppen if more pu lleys we reused?

Ac tivity 7:Sticky situations

You will need : 1/2 cup of skimm ed milk, 2 tb sp vinegar, 3 large c ups or be akers, 1 c offe e filter

a p lastic spo on, pa per towe ls, 1 tsp ba king pow der,

water

Put the m ilk and vineg ar into a c up tog ethe r and stir

for ab out a minute. The lumps that fo rm a re c a lled

c urds a nd the rem aining liquid is ca lled whe y.

Sep ara te the c urds and whey b y straining the m ixture

through a c offee filter/ pa pe r towe l into a c up.

Sc oo p the c urds out from the filter and d ry them o ut

by gently squeezing the m w ith a p aper tow el until

they feel firm. Put the c urds into a nothe r c lea n cup ,

stir in 2 tsps of w ater and then add the b aking

pow der. Now a dd very sma ll amo unts of wa ter until

it looks like g lue.

You c an te st the stickiness of your glue in the next a c tivity.

S

Paper plate

Cup of pennies

Paper clip

Glued strip of card

S

Paper plate

Cup of pennies

Paper clip

Glued strip of card


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Ac tivity 8:How sticky?

You will need : Different type s of g lue, inc lud ing your hom em ade g lue a nd som e p ea nut

butter/ho ney, pa per plates, a ho le punc h, pa per cup s, string, large pap er clips, lots of p ennies/

sma ll we ights

To ma ke your glue te sting eq uipm ent first c ut a strip of c a rd , ab out 5cms wide , all the w ay

ac ross a p aper p late. Punch a ho le a t ea c h end of the strip a nd fo ld it into thirds.

Sprea d som e o f the g lue you wa nt to test on the m idd le third of your strip and glue it to the

bo ttom o f a pa pe r plate. Do this on a sep arate p late for eac h type of glue you wa nt to test

ma king sure you use e qua l amo unts of g lue ea c h time. For the b est results, let the g lue d ry for

about 30 minutes.

Punch tw o holes on either side of a pa pe r cup and tie ea ch e nd o f a p iec e of string to ea c h of

the ho les in the c up . The string shou ld ma ke a ha nd le fo r the c up . Twist a p aper clip into a n S

shap e a nd a ttac h one e nd to the string ha ndle on your c up a nd the o ther end to the two ho lesin the strip of c a rd (onc e the glue ha s d ried ).

Hold your paper p la te off the g round so tha t the c up d oe sn t rest on a surfac e. Now c ount the

numb er of pennies/ we ights you can p ut into the c up b efore the strip p ulls awa y from the p ape r

plate.

How ma ny pe nnies c an ea c h g lue ho ld? Whic h g lue is the stic kiest?

Activity 9:Hom e shap es

You will need : penc il, c rayons or pa int, pa p er

Take a loo k at your house. What sort of sha pes is it ma de up of? Rec ta ng les, triang les,

squa res? Try d rawing your house b y drawing the largest sha pe first and the n filling in all the

other smaller sha pes and deta ils.

Next, draw a p ic ture o f how your d rea m ho use w ould look. Think ab out w ha t sort of style you

wo uld like your house to be, for exam ple, a me d ieva l ca stle, a skysc raper or a c ountry c otta ge .

What w ould yo u like to put in your house? Would it have a swimm ing poo l or tennis c ourts?

What wo uld it be ma de of?

Ac tivity 10:How does a b uilding feel?

Ac t out the d ifferent p a rts of a build ing and feel the force s that a rc hitec ts and eng inee rs must

co ntend with!

Be a c olumn b y ba lanc ing a pile o f boo ks on your hea d. Be a cantileve r (a struc ture, such a s a d iving boa rd or a ba lc ony, that is only supp orted a t

one end ) by holding out a pile o f bo oks at arms length.

Be a n arch, with two p eop le, by lea ning a ga inst ea c h othe r s hand s.


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Think about w ha t force s you a re feeling . Are you in tension (be ing stretc hed ) or c om pression

(be ing squashed )?

Think ab out w hat othe r struc tures you c ould m ake for exam ple; a tunnel, a dom e o r a

suspension b ridge . Ca n you ma ke a w hole build ing?

Ac tivity 11:Tough balloons

You will need : Ba lloo ns filled with a ir, ba lloons filled with w ater, sticky ta pe, 4 30cm x 30cm

piec es of thic k c ardb oa rd from a c ardb oa rd b ox

NB: Make sure yo u ha ve som eo ne w ith you when testing this expe riment to

ma ke sure you d o not fa ll. Also , make sure yo u test your wa ter filled

ba lloo ns outside o r som ew here that you c an ge t we t!

Ma ke two strong p la tforms by g luing tw o p iece s of c a rdboa rd tog ethe r so

that the c orruga ted lines in the ca rdbo ard a re going in op posite

d irec tions. This should m ake it extra strong .

Sta rt by sta nd ing on o ne o f your p latfo rms sup ported by the b a lloo ns filled with a ir. The b a lloons

stay in plac e b etter if you ta pe them o nto the b ottom platform a nd then p ut the sec ond

p la tform on top . Have a friend pop one b a lloo n at a time. How few b alloo ns still support your

weight?

Do ba lloo ns filled w ith wa ter hold your we ight better or wo rse tha n ba lloo ns filled with air? Why

do you think one wo rks bette r than the othe r?

Ac tivity 12:Strong shapes

You will need : Toothp icks, jelly swee ts (mid get gem s work we ll!)

Ma ke a va riety of sha pes, suc h as a squa re o r a triang le, from the swe ets and toothp icks by

p lac ing one swee t in ea c h of the c orners. Press the sides and c orners of ea c h of the sha pes.

Which sha pe is the strong est?

Which shape d o you think would b e b est to use to c onstruc t a building?

Activity 13:Spaghetti Towers

For eac h group you will need : 50g of d ried spaghet ti (approx 50-60 strand s), supp ly o f

mini-marshmallows

This ac tivity wo rks best as a c om pet ition betw ee n group s of 2 5 peop le. Eac h group must

construct a n unsup ported spaghet ti tower. The spaghet ti is used as the struts and wa lls and the

ma rshma llow s a re used to c onnec t the joints. The highest towe r wins!


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Top tips: Think ab out the results of a c tivity 12. Which w as the strong est sha pe? Can you use th is

shape to he lp b uild your tow er? Co uld you c om b ine shape s to make a tow er tha t is both ta ll

and strong ?

Ac tivity 14:Foam hom es

For eac h group you will need : 1 plate, 1 or 2

bow ls, 1 ha nd mixer and / or elec tric m ixer, 1 ruler,

wa shing up liquid, wa ter. Op tiona l: spoo ns or lolly

stic ks

This ac tivity wo rks best in g roup s of 2 -3 peo p le.

The c ha lleng e is to b uild a tow er of foa m a t least

30c m high a nd no m ore than 25c m a c ross itsbase. You may not use any supports other tha n

the foam itself. You c an alter the c onsistenc y of

the foa m b y either ad ding m ore w ashing up

liquid or by wh isking your foa m faster or for long er.

Which tea m c an m ake the highest tow er?

What typ e o f foam ma kes the b est struc ture: light and fluffy; dense a nd strong ; or

ma ybe a c omb ination of bo th?Ac tivity 15:Bridging the gap

You will need :4 or 6 bo oks (to make tw o sta c ks of eq ua l height ), ca rd , sc issors, lots ofpennies or sma ll we ights

Ma ke two stac ks of bo oks of the same he ight a nd m ake sure they a re a bo ut 10cm a part. La y

one p iece of c ard a c ross the b oo ks and m ea sure how m any pennies it c an ho ld be fore it

collapses.

Try this expe riment a ga in and try d ifferent tec hnique s to streng then your b ridg e. You c an tryfolding your c a rd in half, p lea ting your c a rd , or you co uld even ma ke an arch. You c an do this

by cutt ing two slits into the e dge s of your ca rd , pushing the flap s unde r the e dge of your book

c ove rs and pushing the boo ks together slightly.

How ma ny pe nnies c an the strong est b ridge hold?

Ac tivity 16:Build like a beaver

You will need : A long , clea r c onta iner, sand , grave l, p lasticine o r c lay, ic e lolly sticks and a

buc ket of water


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Fill your c onta iner with sand and d ig the c ourse o f a river throug h it. Choose a go od p lace for

your da m and c onstruct it using the ice lolly sticks, clay a nd gravel. Your da m should still let a

little b it of wa ter throug h but no t too muc h. How c ould you make your da m struc ture strong er?

What shape d o you think it should b e?

Test you da m b y em ptying a b uc ket of wate r dow n your river. Did your dam hold b ac k thewater?

Ac tivity 17:Cantilever fever

You will need : Newspaper, ma sking ta pe, string, a p lastic c up or yoghurt po t, pennies or small

weights

A c antileve r is a structure tha t is only supported a t one end ,

suc h as a d iving b oa rd , a b oo k shelf brac ket, or a tree b ranch.They a re a lso o ften used in b ridg e c onstruc tion.

How far out from a wa ll, or tab letop , ca n you b uild a c antilever

structure w ith the ma teria ls p rovided ?

Next, try to make a c antilever that reac hes 50c m o ut from the

wa ll or ta b letop . How c an you streng then this structure? You c a n test the strength of your

c antilever by a ttac hing a piec e o f string to your c up a nd ha nging it from the end of your

c onstruc tion. How m any penn ies c an your structure hold?

Ac tivity 18:Invent a tent

You will need :4 stra ight twigs (ab out 30c m long ), string or a rubb er ba nd , pa per (preferab lyb row n p aper), sc issors, a p enc il, sticky tape, dec orat ions

Tie your twigs together, quite loosely, about 7 or 8cm s from the top . Arrange the

twigs so tha t they form a c onica l shape d frame .

Using a piece of sc rap pa pe r and a pe ncil, trac e the outline o f one o f

the t riang ular sides of your tep ee frame and cut this out fo r your

template.


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Next, stretc h out a la rge piec e of p ap er and trac e a round your tem p late four time s so tha t the

long ed ge s of the triang les a re to uching. Cut this shap e o ut and ma ke a sma ll hole in the

botto m o f one of the short sides for a d oo r. Dec orate the p iec e of p ape r how ever you wish.

Fold the p ap er along the long pe nc il lines and ta pe the edge s up to ma ke your cove r for your

tep ee . Next, cut the tip o f the cove r off for the tw igs to fit throug h. Onc e this is on, you ca n

tape the twigs into p lace o n the inside c orners of the c ove r.

Ac tivity 20:Crea ture com forts

Do som e resea rch on how d ifferent a nima ls build the ir houses and p resent your find ings on a

poster. You c ould think about o ne o f the follow ing ide as or you c ould use your own:

A be e hive

A b ird s nest

A termite mo undA c add is fly la rvae c ase

A b ad ge r set

What sorts of ma teria ls a re used to b uild the hom e? How are they construc ted ? Are they

ma de b y one a nima l or a re they ma de a s a g roup ? What size a nd shape struc tures do they

build?

Organisers notes

Ac tivity 1: A question o f balanc e

Gravity ac ts on a ll ob jec ts on Earth. The a verage loc at ion o f an o bjec t s we ight , and the p oint

a t which the e ffec t of g ravity seems to b e c onc entrated , is c a lled the c entre of gravity. An

ob jec t can be b a lanc ed if it is supp orted d irec tly below this c entre of gravity.

If an o bjec t has a low c entre of g ravity it tend s to b e

sta b le and w ill no t fall over ea sily. When the c ent re of

gravity of an o bjec t is high it b ec om es mo re unsta b le

and is mo re likely to to pp le. If the cent re of g ravitymo ves outside the bo undaries of the b ase; the ob jec t

will fa ll over. For exam p le, it would b e e asier for a

doub le-de c ker bus (high c entre of gravity) to b e p ushed

over on a windy roa d than a c ar (low c entre o f gravity).

This is bec ause it ta kes less effo rt to move the high

c entre of g ravity outside the bound aries of the b ase o f

the vehicle.

High centre of gravityHigh centre of gravity

Low centre of gravityLow centre of gravity


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Ac tivity 2: Whats long and sticky?

When you b a lanc e the stick on your ha nd it will rota te a round its c ent re of g ravity. The further

awa y the w eight is loca ted from the axis of rota tion (suc h as your hand ), the slowe r the stick

turns. When the we ight is a t the top of the stick this rota tion is slow eno ugh to c orrec t the

mo vem ent quickly and the b a lanc e is ea sily ma inta ined . When the weight is at the b otto m of

the stic k the rota tion is muc h q uic ker and it is muc h ha rder to b a lance.

Ac tivity 3: Lift up a grown up

A lever is ma de up of three imp ortant p a rts tha t a re ne c essa ry for it to wo rk; a fulc rum (a p oint

a round wh ich the lever turns or pivots), a load (the things you a re trying to lift or move) a nd the

force app lied to the leve r. In this c ase; the p lank is the leve r, the b lock is the fulc rum, the a dult

is the load and you are the forc e trying to move the load .

Leve rs a re used to he lp you move a la rge loa d with a sma ll force . The further awa y the force

(child ) is from the fulcrum the ea sier it is to m ove the loa d (ad ult). If the fo rc e c rea ted b y a

c hild , at a la rge d istanc e from the fulcrum, is bigg er than the fo rce o f an a dult, at a short

d ista nce from the fulcrum, then the c hild will be a b le to lift the a dult.

Ac tivity 4: Flying c ornflakes

In th is expe riment ; the lolly stick is the lever, the penc il is the fulc rum, the c erea l is the load and

you are the forc e. If you p lac e the c erea l at o ne end of the lolly stic k and plac e the p enc il

c lose the op posite e nd; whe n you hit the leve r the c ereal should m ove the g rea test d ista nce. If

you want to try and ge t the cereal into your co ntainer you m ust try to hit your lever with exac tly

the sam e forc e ea c h time .

Ac tivity 5: Stac k Attac k

When you b a lanc e the top bloc k of the sta c k, the c entre of g ravity of this b loc k rests on the

ed ge o f the sec ond b loc k be low. When you balanc e the top tw o b loc ks; the ce ntre of gravity

of those two b loc ks c om b ined wa s ba lanc ed on the third b loc k. Every time you move a new

set o f b loc ks, the c entre of g ravity of the growing g roup of b loc ks wa s positioned on the ed ge

of the bloc k be low .

Ac tivity 6: Do less work!

A p ulley is a simp le m ac hine made o ut o f rop e, or string, and a whee l (or in this c ase a rolling

p in). Pulleys cha nge the d irec tion of the force a pp lied in orde r to lift an ob jec t. This me ans we

pull dow n instea d of up therefo re m aking it ea sier to lift a s you c an use your bod y as a

counte rwe ight . With ea c h add itiona l pulley add ed to the system , the weight is ea sier to lift. If

you ha ve tw o p ulleys you c an lift twice as muc h we ight as if there w as no p ulley a t a ll. If you

have three pulleys then you c an lift three time s as muc h a nd so on.

Ac tivity 7: Sticky situa tions

Milk is made o f solids and wa te r. Ab out 3.5% of the solids a re p rote ins. There a re tw o d ifferent

type s of p rote ins: c asein and whe y. When you m ix the m ilk and vineg ar tog ethe r, the a c id in

the vinegar ma kes the c asein in the m ilk stick together to fo rm the sma ll white lumps (curds).

Simple m ilk curds c an a lso b e c om b ined with che mica ls and then ha rdened into p lastic s.

Ca sein is used to ma ke c om bs, jew ellery, eve n som e house p a ints. Casein g lue in pa int is wha t

makes it stick to your wa lls and c eiling s.

Ac tivity 8: How sticky?

When your glue is app lied to the paper plate, the p rote ins in your glue either c onne c t to

mo lec ules of the c a rd or flow into the c ard s pores and spaces. As the liquid in the g lueeva porates the p rote ins bec om e ha rdened . This ma kes the p iec es of c ard stic k toge ther. If you

had tested your glue on a ma terial, suc h as polished me ta l or glass, instead o f your paper


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p late , then the g lue wo uld no t ha ve stuc k as efficient ly. This is bec ause these typ es of m a terials

do no t have a s ma ny po res or spac es for the g lue to attach itself to.

Ac tivity 9: Hom e Shap es

Architec ts wo rk very hard in designing the perfec t b uild ing for their c lient . To d o th is they must

think of wha t the building will be used for, how ma ny pe op le it is me ant for, the c ond itions of

the b uild ing site a nd which build ing ma teria ls will be the m ost a pp rop ria te.

Architec ts a lso ne ed to c onsider how the build ing will look. What typ es of c olour will they use?

What sha pes and forms will be used ? Should the b uild ing b lend in or sta nd out? Will it be p lain

or will it b e fa nc y?

Think about the d ifferent styles of b uild ings in different countries. How wo uld a house in a ho t,

desert country differ from a house in a c old, ic y co untry? What d ifferenc es wo uld you expec t in

structures built on swa mp y ground or on mounta in terra in?

Ac tivity 10: How d oes a b uilding feel?

Struc tures such a s c olumns a re und er co nstant c om pression a nd need to b e m ad e o ut ofma teria ls tha t can tolerate these c ond itions suc h as b rick, stee l or reinforce d conc rete .

Ca ntileve rs need to b e very strong so tha t they can resist bend ing a nd b rea king. When a

structure is being bent it is being c om pressed on one side and in tension on the other. This

me ans cantilevers nee d to b e m ad e o ut of a ma teria l tha t is strong in both te nsion a nd

c om pression suc h as steel or aluminium.

An a rc h uses c om pression to balanc e its ow n we ight a nd the w eight p iled on to p of it (for mo re

informa tion see notes for ac tivity 15). Ma terials suc h as c onc rete o r c ast iron a re o ften used to

ma ke arc h bridge s.

Ac tivity 11: Toug h balloo ns

A gas is ma de up of a tom s surround ed by la rge am ounts of spac e. This me ans tha t a ga s c an

be c om pressed into a sma ller a rea or volume . In a liquid the a tom s are muc h c loser toge ther

and the volume of a liquid ca nnot be reduced .

When you sta nd on the b a lloo ns filled with a ir you squa sh the ba lloo ns and the gas inside

squashes a long w ith it. When you sta nd on the ba lloo ns filled w ith wa ter the vo lume inside

ca nnot b e red uce d and the b alloon ha s to stretc h outwa rds c ausing it to po p.

The mo re ba lloo ns there a re unde r the p la tform; the ea sier it b ec om es to supp ort your weight.

As the b a lloo ns a re squashed dow nwa rds the surfac e a rea of the b a lloo n touc hing thep la tform increa ses. This me ans tha t you a re sprea d ing your weight over a muc h la rger surface

a rea and reduc ing the pressure on ea c h individual ba lloo n.

Ac tivity 12: Strong shap es

You should find tha t the triang le is the strongest shape a s it does not t end to b end or buc kle.

The squa re is quite we ak as it often b rea ks a t the joints but c an be strengthened w ith the

add ition o f a d iago nal suppo rt (therefore c rea ting two triangles). A lot of b uild ings use triang les

in their structures, such as the roof and walls, because they are so strong.

Ac tivity 13: Spaghetti Towers

From ac tivity 12) you c an te ll tha t triang les a re the strongest shape. It is possible to build atowe r ou t of only squa res but this structure w ill no t be ve ry strong a nd wo uld b e q uite wigg ly.

Structures built from only triang les wo uld b e a lot stronger but w ill use up a ll of your ma terials


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before your tow er gets very tall. The b est wa y to b uild a ta ll tow er would b e to use a

c om b ina tion of t riangles and squares.

Even though the towe r is sta nd ing still, the individua l pa rts a re a lways pushing and pulling

aga inst ea c h othe r; they are e ither in tension o r under co mp ression. Ima gine ta king the p lac e

of one of the piec es of your tower; would you fee l squashed or stretc hed ? The vertic al piec es

of spaghet ti in your tower will be in co mp ression, and this force will be g rea test a t the base o fthe towe r. The ho rizonta l and d iago na l p iec es of the to we r ma y be in tension.

Ac tivity 14: Foa m home s

Think abo ut building a rea l tow er. Where would you need the tow er to b e the strong est? At

the top or the b ottom ? Ta ll build ings req uire strong, fla t founda tions tha t w ill shoulder the

we ight of the building. By making the b ottom o f your tow er out of thick dense foa m you a re

rec rea ting the found a tions of a rea l build ing. This strong base shou ld b e the best structure to

hold the rest of your tower ma de o ut of light fluffy foa m.

Ac tivity 15: Bridg ing the g ap

In this experime nt the w ea kest type of b ridge should ha ve b een the simp le p iece of c a rd ac rossthe g ap . This is the equivalent of a bea m bridge, suc h a log ac ross a stream. This type of

b ridg e relies on the streng th o r stiffness of the m a terial la id a c ross the gap . If the c a rd , or log,

sta rts to b end then it ma kes a very bad b ridge . If you fold the c ard in half, or into a square

bea m, then the b ridge should ho ld mo re w eight, as the c a rd will be strong er, but the b ridge will

still be gene ra lly we ak.

Arc hes we re made b y Rom ans hundred s of yea rs ago and ha ve g rea t na tura l streng th. Arches

use a c urved structure which provides a high resista nc e to bend ing forc es. When a we ight is

p lac ed on top of a n a rc h the forc e is transferred to the sides which b eg in to push outw ards.

Sup ports a t the side of the b ridg e, ca lled buttresses or a butments , or in this c ase the b oo ks,

push b ac k on the sides to ma ke the struc ture strong er and prevent the bridg e from buc kling.

If you try p lea ting your p iece o f ca rd , i.e. folding it so tha t it loo ks like a fla t fan; then the b ridg e

should b ec om e very strong . A plea ted c ard a c ts like a row o f triang les and the se triangles

effe c tively inc rea se the thickness of the c a rd . This struc ture is extremely resista nt to buc kling

and b end ing. You c an ma ke this p lea ted ca rd even strong er b y sec uring the e nds of the V-

shaped c hannels so tha t it do es not flatten o ut whe n a w eight is plac ed on it.

Ac tivity 16: Build like a bea ver

There are many ways to improve the streng th of your dam. One c om mo n type o f da m is c a lled

an arch d a m. This is a structure which has a c urved surfac e wh ich fac es the w a ter. When the

wa ter p resses on the d am the a rch streng thens the structure.

Som e d ams rely on the ir sheer we ight to ho ld the w a ter bac k. These a re c a lled gravity dams .

Other da ms a re p rop ped by gian t supports ca lled b uttresses, so c a lled buttress dams . To

streng then your ow n dam yo u c ould e mp loy a ll of the se te chniques, e.g., an a rc hed struc ture;

a hea vy struc ture, which wo uld b e d ifficult to mo ve; or by using supp orts to prevent your dam

from moving.

Ac tivity 17: Cantileve r feve r

For this experime nt you should find tha t the further aw ay from the e dge of the ta ble you ha ng

your we ights the ea sier your struc ture will break. This is due to a force ca lled to rque , a

rota tiona l force tha t increa ses with d ista nce from the fulcrum (in this c ase the e dge of thetab le). For examp le, if you were hang ing from a tree b ranch you would b e a lot sa fer hang ing

c lose to the trunk than right at the e nd . The further aw ay from the trunk you a re ha nging, the


13/15


grea ter the torque a nd the m ore likely you are to b rea k the b ranch and fall.

One wa y to streng then your ca ntilever might b e to ma ke the b ase o f the struc ture thicker. This

wo uld m ea n that the c entre of gravity, and m ost of the weight of your struc ture, would b e

c loser to the fulcrum a nd there wo uld be less torque a c ting o n the c antilever. So, to c ontinue

with the tree examp le, if the b ranc h you we re ha nging from had a thic k and heavy b ase, you

wo uld be a lot sa fer than if the b ranc h wa s the sam e thickness the w hole wa y along .

Anothe r wa y to inc rea se the streng th o f your struc ture w ould b e to use a vertica l suppo rt a t the

base o f your cantilever and tie a string, or wire, betwe en the to p o f the supp ort and the end o f

the struc ture. This wo uld red uc e the tension on the to p o f the structure and the c om pression o n

the bottom . If you tied a p iec e of rop e betw een the end of your branch a nd the tree trunk

then the b ranc h wo uld be a lot m ore sec ure.

Ac tivity 18: Invent a tent

Tep ees a re just one examp le of the type of hom e tha t an Am eric an Ind ian ma y have b uilt. In

this type of soc iety, the houses that we re b uilt were not o nly co nstruc ted bec ause the y co ped

we ll with the c lima te and suited the ir nee ds, but a lso b ec ause o f soc ial rea sons. The sizes ofhouses we re o ften d ete rmined by the soc ial sta tus of the person w ho w as going to live in it, for

examp le, a tribe lead er would ha ve a la rge r house tha n a tribe mem ber. All the b uild ings,

how ever, we re c onstruc ted from loc a l materia ls tha t were ea sy to find such a s ba rk, wo od ,

roc ks, ree d s, grass, ea rth, snow , and other na tural ma teria ls a t ha nd .

In extreme ly cold we a the r the ir outside , slanting wa lls might b e p iled with snow , the interior

c ould b e floored w ith soft leave s or branches, and a fire c ould b e p lac ed inside w ith the smo ke

esc ap ing from the ho le in the roo f. In the summe r, fam ilies ofte n move d into a irier houses,

c oo king outside b enea th a porch-like struc ture.


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