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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

slide8

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.
slide15

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.
slide19

Third Class Lever

Input force

Output force

slide20

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

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.
slide30

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.
slide32

3

1

1

2

2

slide39

A

b

c

Efficiency?

slide40

c

b

A

slide41

A

b

slide43

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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