Lever Systems Lever systems Objectives 1 Identify the

Lever Systems

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. 4. Identify the effect of friction on an object when it is being moved. 5. Communicate using correct science terminology when discussing lever systems in general and specific terms.

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 Definitions Continued Effort Arm – The part of the lever to which the effort force is applied. 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. Lever C. Resistance Distance B. Fulcrum D. Resistance Force E. Effort Arm G. Effort Distance F. Effort Force H. Resistance Arm F G C E D A H Entire board B

Classes of Levers Effort Resistance Fulcrum First Class Lever

Classes of Levers Effort Resistance Fulcrum Second Class Lever

Classes of Levers Effort Resistance Fulcrum Third Class Lever

You Label! Second Class Lever E R F

You Label! First Class lever E R F

You Label! Third Class Lever E R F

Classes of Levers Examples Third Class Lever R E F

Classes of Levers Examples R F E First Class Lever

Classes of Levers Examples First Class Lever

Classes of Levers Examples Third Class Lever

Classes of Levers Examples Second Class Lever R F E

Classes of Levers Examples Second Class Lever

of Levers Examples Classes of. Classes Levers Examples

Classes of Levers Examples First Class Lever

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

Lever Force and Mechanical Advantage Formulas Mechanical Advantage = Effort Distance / Resistance Distance MA = Ed / Rd Effort Distance = Mechanical advantage x Resistance Distance Ed = MA x Rd Resistance Distance = Effort Distance / Mechanical Advantage Rd = Ed / MA These formulas are all dirivations 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 Mechanical Advantage = Effort Distance / Resistance Distance MA = 3 / 1 = 3 Effort Force = Resistance Force / Mechanical advantage EF = 120 N / 3 40 N EF = _______

Lever Force and Mechanical Advantage Formulas Effort Force = Resistance Force / Mechanical Advantage Ef = Rf / MA Resistance force = Effort Force x Mechanical advantage Rf = Ef x MA Mechanical Advantage = Resistance Force / Effort Force MA = Rf / Ef These formulas are all dirivations 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! ? Rf = Ef x MA MA = 4 Rf = 40 g

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

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

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

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

Effect of Pulling Up, Down, Or Straight Three Kinds of Friction Sliding Friction –Two surfaces sliding against each other. Rolling Friction – one surface rolls over another surface. Fluid Friction – When a lubricant is used between to objects that are sliding over each other.

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. 4. Identify the effect of friction on an object when it is being moved. 5. Communicate using correct science terminology when discussing lever systems in general and specific terms.