What is mechanical advantage?What is mechanical advantage?The force you apply to a machine is The force you apply to a machine is called the called the effort force effort force (input force)(input force)The force that the machine applies The force that the machine applies is the is the resistance force resistance force (output (output force)force)To open a can, you apply a force of To open a can, you apply a force of 50 N to the can opener. The can 50 N to the can opener. The can opener applies a force of 775 N to opener applies a force of 775 N to the can. the can. The machine multiplies your effort The machine multiplies your effort force so work becomes easierforce so work becomes easierA machine lets you use a small A machine lets you use a small force to overcome a large forceforce to overcome a large forceThe number of times a machine The number of times a machine multiplies the effort force is called multiplies the effort force is called its its mechanical advantagemechanical advantage

How to calculate mechanical How to calculate mechanical advantage:advantage:

MA = resistance force MA = resistance force ÷÷ effort force effort forceThe The resistance forceresistance force is often is often equal to theequal to the weight weight of an object being movedof an object being movedEX:EX: To crack a pecan, you apply a force of To crack a pecan, you apply a force of 50 N50 N to to the nutcracker. The nut cracker applies a force of the nutcracker. The nut cracker applies a force of 750 N750 N to the pecan. What is the to the pecan. What is the MAMA??MA = RF MA = RF ÷ EF÷ EFMA = 750N MA = 750N ÷÷ 50N 50N MA = 15 MA = 15 (no units used)(no units used)The The higher higher the mechanical advantage, the the mechanical advantage, the easier easier workwork is! is!

Calculate Mechanical Advantage:Calculate Mechanical Advantage:You apply a force of 100 N You apply a force of 100 N to a pulley. The pulley to a pulley. The pulley applies a force of 800 N to applies a force of 800 N to lift a boulder. What is the lift a boulder. What is the mechanical advantage?mechanical advantage?

MA

RF

EFX

÷ ÷

How to determine MA of a lever How to determine MA of a lever Every lever has two parts, an Every lever has two parts, an effort armeffort arm and a and a resistance armresistance armThe The effort armeffort arm is the distance from the is the distance from the effort force to the effort force to the fulcrumfulcrumThe The resistance armresistance arm is the distance from the is the distance from the resistance resistance force to the fulcrumforce to the fulcrumMA = effort arm length/ resistance arm length

(input)

(output)

Finding MA for a Fixed PulleyFinding MA for a Fixed PulleyFixed pulleys only change Fixed pulleys only change direction of the effort force, direction of the effort force, not the amountnot the amountThe The effort forceeffort force is is equal equal to to the the resistance forceresistance forceAs a result, the As a result, the MAMA of a of a fixed pulley is always fixed pulley is always equal equal toto 11

Ex:Ex: If the effort force = If the effort force = 20 N20 N and the Resistance force = and the Resistance force = 20 N20 N, what is the MA? , what is the MA? MA = RF MA = RF ÷ EF ÷ EF MA = 20N MA = 20N ÷20N ÷20N MA = 1MA = 1

A fixed pulley’s MA always = 1

Finding MA for Moveable Pulleys and Finding MA for Moveable Pulleys and Pulley SystemsPulley Systems

You can find the MA of a You can find the MA of a moveable pulley by moveable pulley by counting the number of counting the number of ropesropes that lift the that lift the resistanceresistanceA A pulley systempulley system is made is made up of both fixed and up of both fixed and moveable pulleysmoveable pulleysThe pulleys are used The pulleys are used together to together to increase the increase the MA of the systemMA of the systemThe The MAMA of a pulley of a pulley system is system is equal to the equal to the number of supporting number of supporting ropesropes

MA = 2

The The MAMA of a pulley system is of a pulley system is equal to the number of equal to the number of supporting ropessupporting ropes

Determine the MA of each pulley system:Determine the MA of each pulley system: MA = 2 MA = 3 MA = 4

Finding MA of an inclined plane Finding MA of an inclined plane (ramp)(ramp)

You can find the mechanical advantage of an inclined You can find the mechanical advantage of an inclined plane by dividing its length by its heightplane by dividing its length by its height

MA = length / heightMA = length / height

MA = 3 m / 1 mMA = 3 m / 1 m

MA = 3MA = 3

Length

Height