Problem
Youclimbtheladderandstepinside.It’syourfirsttimeinyourfriend’streehouse.Ithasjustabouteverythingyoucouldwant.Exceptsnacks!“Oh,IknewIforgotsomething,”saysyour friend.
Justthen,yourfriend’sgrandmothercomesoutofthehousecarryingtwolunchbags.Buthowwillshegetthemupto you?
Solution
Grandmahasaropeandabucket.Sheswingstheropeoveratreebranch.Thenshetiestheendoftheropetothebucket handle.
Grandmaplacesthelunchbagsinthebucketandpullstheotherendoftherope.Witheachpull,thebucketgoeshigher.Soon,itreachesyou.Problem solved!
It's Simple
Grandmausedtheropeandbranchasasimplemachine. Simplemachineshelpusdowork.Theymovethingsfaster,farther,ormoreeasilythanwecanwithout them.
Simplemachineshavenomorethanafewparts.Somehavejustone part.
IntheGroove
Howcanaropeandabranchbeamachine? Together,theyformapulley.A pulleyisawheel.Ithasacordwrappedaroundit.Thecordfitsinagroovearoundthewheel.Thewheelturnsasthecordispulledthroughthe groove.
Thebranchdoesn’thaveagroove.Itdoesn’tturnlikeawheel.But,theideaisthesame.Grandmapulleddownononeendoftherope.Thentheotherendmovedup.Thepulleymadeiteasiertoliftthebucket.Itchangedthedirectionofthe force.
Howto liftthingswithapulley
1
Pulldownonthisendofthe rope.
2
Theropemovesthroughthe pulley.
3
Theloadmovesupwith thisendofthe rope.
