Problem

Youarecampingwithyourfamilyandyourbestfriend.You’vehadadayoffun.Nowyoulookforwardtoanightnexttoablazingcampfire.Andit’syourturntohelpstart it!


Youandyourfriendgathersomelogs.Youcrisscrosstheminasmallpile.Youraunttriestolightoneofthelogswithamatch.Nothinghappens.Shesmiles.“Weneedsmallerpiecesof wood.”


Buthow?Thewoodistoohardtobreakapartwithyourhands.“Weneedatool,” yourfriend says.

Solution

Yourememberseeingasmallaxeinaboxofcampingequipment.It’stheperfecttoolforthe job!


Youbringittoyouraunt.Shestandsa log upandcarefullyswingstheaxesothatthebladestrikesthecut wood on top.


THWACK!The logsplitstoitshalfwaypoint.Anotherswing,andCRACK!Itsplitsin two.Afewmorewhacksreducethehalflogstopiecessmallenoughtostartthe fire.


Problem solved!

It'sSimple

Theaxeisagoodtooltosplitwood.It’sasimplemachine.Simplemachineshelpusdojobs.Theymovethingsfaster,farther,ormoreeasilythanwecanwithout them.


Youprobablydon’tthinkofanaxeheadasamachine.Ablenderoracarmightcometomind.Theseareallcomplexmachines.Theyhavelotsof parts.

Simplemachineshavejustafewparts.Somearemadeofonlyonepart.Nearlyeverymachine,however,hasoneormoresimple machines.


Simplemachinescanbecombinedinendlesswaystodotasks.Buteachonehelpsusdoworkallonits own.

force direction axe head log change in direction

AWedgeGivesYouanEdge

Theaxeheadthatyouusedtosplitthewoodisasimplemachinecalledawedge.It’sshapedlikeatriangle.Theheadstartsoutwideandnarrowstoathinedge.The thinnertheedge,thesharperthe wedge.


Howdoesitwork?Itstartswitheffortfromyou.Ittakesefforttoswingtheaxe.Thiseffortprovidestheforcetodrivetheaxeintothe wood.


Swingtheaxe.Theforceisdownward.Astheaxepushesintothewood,thewedgedirectsthatforcesideways.SwingagainandCRACK, thewood splits.

With a powerful CHOP, this axe splits the wood in two.The axe head is a wedge. 

It’sAllAboutTrade-offs

Now,supposeyouhadtwoaxestochoosefrom.Onehasaheadthatislongandnarrow.Theotherisshorterandwider.Whichwouldyouchoose?


Remember,thethinnerthewedge,thesharpertheedge.Thelong,narrowaxeheadwillbesharper.

So,itwillbeeasiertodriveintothewoodwitheachswing.Butithastogodeeperbeforeitsplitsthelog.Theshort,wideaxecouldsplitthewoodwithoutgoinginsodeep.Thismightmeanfewerswings.Buteachswingwouldneedalotmoreforce.You tradedistancefor effort.