Problem
“Wow,lookatallthesebooks!”yousay.It’sBookDonationDayatschool.Students,teachers,andparentshavebeendroppingoffboxesofbooksallmorning.Theboxesarereallyheavy.Howwillyougetthebooks inside?
Solution
Youcomeupwithagreatidea!YougototheMaintenanceOfficeandborrowadollycart.Now,volunteerscanstacktheboxesonthedolly.Thenit’seasiertorolltheboxestothelibrary.Well done!
It's Simple
Whatmadethedollysuchagoodtool?It’ssimple!Thewheelsarepartofa simplemachine.Simplemachineshelpusdowork.Theymovethingsfaster,farther,ormoreeasilythanwecanwithout them.
axle
wheel
axle
Simplemachineshavenomorethanafewparts.Somehavejustonepart.Nearlyeverymachinehasoneormoresimple machines.
Youcanfindwheelsandaxlesonwagonsand bicycles.
MachinesThatGoRound
Ifanobjectturnsinacircle,itisprobablyasimplemachinecalleda wheelandaxle. Awheelisadiscthatturnsroundandround.Anaxleisarod.Itisatthecenterofawheel.Itconnectsthewheeltoavehicle,likeabike.Whentheaxlemoves,sodoesthewheel.Andsodoesthe bike.
Imaginepullinga loadofbookswithoutwheels.Itwouldscrapetheground.Asyoupullforward,the forceoffrictionpullsintheoppositedirection.Wheelsroll.So,thereislessfriction.Withwheels,ittakeslesseffort to pull.