Lever systems Objectives: 1. Identify the three types of levers. 2.Label a lever system with appropriate part indications: 3. Determine the mechanical advantage of various lever systems.

Lever Systems Definitions Lever – A bar that is free to pivot around a center point (Changes direction and/or amount of force). Fulcrum – The fixed point around which a lever pivots (fulcrums can take many shapes). Effort Force – The force applied to a machine to cause motion of an object. (Measured in Newtons N) Resistance Force – The force exerted by an object due to gravity or friction. (Measured in Newtons N) Mechanical Advantage – The number of times a machine multiplies the effort force. (MA = Ed/Rd)

Lever Systems Continued Effort Arm – The part of the lever to which the effort force is applied. Definitions Continued Effort Distance – The length of the part of the lever from the fulcrum to the effort end of the lever. (The length of the Effort Arm.) Resistance Arm – The part of the lever on which the resistance force is exerted. Resistance Distance - The length of the part of the lever from the fulcrum to the resistance end of the lever. (The length of the Resistance Arm.)

Parts of a Lever System A. LeverE. Effort Arm B. FulcrumH. Resistance ArmF. Effort Force C. Resistance Distance D. Resistance Force G. Effort Distance Entire board C D H G F B A E

Classes of Levers Effort Resistance Fulcrum First Class Lever

Classes of Levers Effort Resistance Fulcrum Second Class Lever

Effort Resistance Fulcrum Third Class Lever

You Label! R F E Second Class Lever

R F E First Class lever

R E F Third Class Lever

Classes of Levers Examples F E R Third Class Lever

E F R First Class Lever

First Class Lever

Third Class Lever

F E R Second Class Lever

Second Class Lever

First Class Lever

Mechanical Advantage Mechanical Advantage = Effort Distance / Resistance Distance MA = 3 / 1 = 3

Lever Distance and Mechanical Advantage Formulas Mechanical Advantage = Effort Distance / Resistance Distance Effort Distance = Mechanical advantage x Resistance Distance Resistance Distance = Effort Distance / Mechanical Advantage MA = Ed / Rd Ed = MA x Rd Rd = Ed / MA These formulas are all derivations of the first formula. If you know your Algebra you should be able to solve for any of the individual parts of each equation if the other two parts are known.

Effort Force Needed Effort Force = Resistance Force / Mechanical advantage EF = 120 N / 3 EF = _______ Mechanical Advantage = Effort Distance / Resistance Distance MA = 3 / 1 = 3 40 N

Lever Force and Mechanical Advantage Formulas Effort Force = Resistance Force / Mechanical Advantage Resistance force = Effort Force x Mechanical advantage Mechanical Advantage = Resistance Force / Effort Force Ef = Rf / MA Rf = Ef x MA MA = Rf / Ef These formulas are all derivations of the first formula. If you know your Algebra you should be able to solve for any of the individual parts of each equation if the other two parts are known.

Mechanical Advantage Effort Distance Resistance Distance MA = Ed / Rd = 100 cm / 50 cm = 2

Your Try! ? MA =4 Rf =40g Rf = Ef x MA

You Try! MA =6 Rf =540N ? Rf = Ef x MA

You Try! ? MA =2 Rf =120N Rf = Ef x MA

You Try! ? MA =3 Rf =10N Ef = Rf / MA

You Try! ? MA =1 Rf =60N What is the only advantage to this lever system? It changes direction of motion. Rf = Ef x MA