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Do Now 3 /3/2014. Take 4 sheets from back table Homework – Simple Machine worksheet Test Thursday. Simple Machines. Levers. A lever is a rigid bar that is free to pivot, or rotate, about a fixed point. The fixed point that a lever pivots around is called the fulcrum . .

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Do now 3 3 2014
Do Now 3/3/2014

  • Take 4 sheets from back table

  • Homework – Simple Machine worksheet

  • Test Thursday



Levers
Levers

  • A lever is a rigid bar that is free to pivot, or rotate, about a fixed point.

  • The fixed point that a lever pivots around is called the fulcrum.


Ideal mechanical advantage of a lever
Ideal Mechanical Advantage of a lever

  • I.M.A=

    Distance from fulcrum to input force

    Distance from fulcrum to output force


Input force

Output force

First Class Lever


First class levers
FIRST CLASS LEVERS

  • The Fulcrum (fixed pivot point) is located between the Input and the Output Forces.  A SEESAW.

  • The Input and the Output Forces move in opposite directions.  The Input Down in order to Lift the Load.

  • When the Fulcrum is closer to the Input than to the Output, there is a Loss in Force but a Gain in Speed and Distance.


First class levers1
FIRST CLASS LEVERS

  • When the Fulcrum is closer to the Output than to the Input, there is a Loss in Speed and Distance, but a Gain in Force.

  • When the fulcrum is Midway between the Input and the Output, there is no change in Force, Speed or Distance.

  • Samples of First Class Levers – Seesaw, Crowbars, Scissors, and Claw Hammers.


Output force

Input force

Second Class Lever


Second class levers
SECOND CLASS LEVERS

  • The Output Force is between the Input Force and the Fulcrum.

  • The Fulcrum is at one End of the Lever.

  • The Fulcrum is usually closer to the Output Force, (load).


Second class levers1
SECOND CLASS LEVERS

  • Second Class Levers produce a gain in Force.

  • Samples of Second Class Levers – Wheelbarrow, Bottle Openers, and NutCrackers.


Third Class Lever

Input force

Output force


Third Class Lever

Output force

Input force

Input force

Output force


Third class levers
THIRD CLASS LEVERS

  • The Input Force is Between the Output force and the Fulcrum.

  • Samples of Third Class Levers – Broom, Shovel, Fishing Pole, Baseball Bat, and Tongs.


Pulley
Pulley

  • A grooved wheel with a rope (or a chain, or even steel cable) wrapped around it.

  • You can change the direction and the amount of your input force.


Fixed pulley
Fixed Pulley

  • A pulley that you attach to a structure.

  • Changes the direction of the input force.

  • Does not change the amount of force you apply.

  • Ideal Mechanical Advantage = 1

1


1



Movable pulleys
Movable Pulleys

  • If you attach a pulley to the object that you wish to move.

  • I.M.A= 2

  • The output force is 2 times the input force you exert on the rope.

  • You must exert your force over a greater distance.


1

2


Pulley system
Pulley System

  • The ideal mechanical advantage of a pulley system is equal to the number of sections of rope that support the object.


3

1

1

2

2






A

b

c

Efficiency?


c

b

A


A

b


A

b


Gears
Gears

  • Two or more wheels linked together by interlocking teeth.


Compound machine
Compound Machine

  • A machine that utilizes two or more simple machines.


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