lever systems. definitions lever – a bar that is free to pivot around a center point (changes...
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Lever Systems
Lever Systems
DefinitionsLever – 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.
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. Lever E. Effort Arm
B. Fulcrum H. Resistance ArmF. Effort Force
C. Resistance Distance
D. Resistance Force
G. Effort Distance
Entire board
CD
H
GF
B
A
E
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!
R
F
E
Second Class Lever
You Label!
R
F
E
First Class lever
You Label!
R
E
F
Third Class Lever
Classes of Levers Examples
F
E
RThird Class Lever
Classes of Levers Examples
E
F
R
First Class Lever
Classes of Levers Examples
First Class Lever
Classes of Levers Examples
Third Class Lever
Classes of Levers Examples
F
ER
Second Class Lever
Classes of Levers Examples
Second Class Lever
Classes of Levers ExamplesClasses of Levers Examples
Classes of Levers Examples
First Class Lever
Mechanical Advantage
Mechanical Advantage = Effort Distance / Resistance Distance
MA = 3 / 1 = 3
Lever Force 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
You 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
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.