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Problem
“Wow,lookatallthesebooks!”yousay,asyoulookatallthecardboard boxes.
“Yeah,”yourfriendsays,“buthowarewegoingtogetthemtothe library?”
It’sBookDonationDayatschool.Astrongstormhadsweptthroughtown.Partoftheschoolwasdamaged,includingthelibrary.Noonegothurt,butmanybookswereruined.Sostudents,teachers,andparentsorganizedabookdriveforthe library.
Peoplehavebeendroppingoffboxesofbooksallmorning.Heavyboxesofallsizesarestackedup.Volunteersarereadytobringthebooksinside.Buttheboxesarereallyheavy.It'stoofartopushordragtheboxes.Howwillyougetthebooks inside?
Solution
Youthinkforamoment.“I’vegotit!Comeon,wehavetogototheMaintenance Office.”
Fiveminuteslater,youandyourfriendcomewalkingdownthehallwaypullingtwodollycarts.Thevolunteerseasilystacktheboxesonthedollies.Thenit’seveneasiertorolltheboxestothelibrary,unloadthem,andheadbackformore.Everyoneisworkingtogethernowthattheyhavetherighttools.Well done!
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It's Simple
Whatmadethedolliessuchgoodtoolsformovingtheheavyboxes?It'ssimple!Thewheelsonthedollyarepartofa simplemachine.Simplemachineshelpusdowork.Theymovethingsfaster,farther,ormoreeasilythanwecanwithout them.
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axle
wheel
axle
Simplemachineshavenomorethanafewparts.Somehavejustonepart.Nearlyeverymachinecontainsoneormoresimple machines.
Thinkaboutaschoolbus.Thedoor’shingesarelevers.Thesetofstairsyouclimbtogetinsideisatypeofinclinedplane.Theseareexamplesofsimple machines.
Youcan findwheelsandaxlesonwagonsand bicycles.
MachinesThatGoRound
Ifanobjectturnsinacircle,it'sprobablyasimplemachinecalledawheelandaxle.Awheelisadiscthatturnsroundandround.Anaxleisarodconnectedtothecenterofawheel.Theyrotate together.
Imaginepullingaloadofbookswithoutwheels.Thebookswouldscrapetheground.Asyoupullforward,theforceoffrictionpullsintheoppositedirection.Wheelsroll.So,thereislessfriction.Andittakesless efforttopullthe books.