Simple Machines: Beyond the piano we talked about yesterday.

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Simple MachinesBeyond the piano we talked about
yesterday.
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Mechanical Advantage

• The ratio of the output and input forces that are
  used within a machine.
• MAeffort arm/load arm
• The effort arm is the distance from the fulcrum
  to the force used to lift an object.

Effort Arm
Force
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Mechanical Advantage

• The load arm or resistance arm is the distance
  from the fulcrum to the object being lifted.

Load Arm
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Mechanical Advantage Math

• If the distance from the fulcrum to the person
  lifting is 1.6 meters, the distance from the
  fulcrum to the object being lifted is 0.4 meters
• MA1.6/0.44
• This means that a person can lift something four
  times heavier than normal

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Levers

• There are three classes of levers

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First Class of Lever

• The fulcrum is in the middle and the effort arm
  and resistance arm are on opposite sides.
• When the force pushes down, the item goes up.
• The MA is one.

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Second Class of Levers

• The fulcrum is at the end
• The object (load) is in the middle and the person
  lifting is at the other end of the lever arm.
• When the force pulls up, the object goes up.

Effort
Load
Fulcrum
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Third Class of Lever

• The fulcrum is at the end.
• The person lifting is somewhere in the middle and
  the object being lifted is at the other end of
  the fulcrum arm.
• When the force pulls up, the load goes up.
• The MA is less than one, but moving the load arm
  and effort arm closer together increases the MA.

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Third Class of Lever
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Wheel and Axel

• A larger wheel connected by a smaller cylinder or
  axel.
• The axel is fastened to the wheel so they turn
  together.
• The wheel moves a greater distance than the axel
  but requires less force.
• The axel moves a shorter distance but requires
  more force.

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Wheel and Axel
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Wheel and Axle

• A wheel and axle is really two machines in one
• The first part is the wheel, it reduces friction
  when rolling something
• Only part of the wheel touched the ground so
  there is not a lot of friction
• The bigger the wheel, the easier it is to move it.

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Wheel and Axle

• The larger wheel (on the outside) rotates around
  the smaller wheel (on the inside).
• The effort or resistance force can be applied to
  either wheel.
• The wheels can have a solid axle in the middle.

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Wheel and Axle

• Because the wheel is larger than the axle, it
  always moves through a greater distance then the
  axle.
• A force applied to the wheel is multiplied when
  it is transferred to the axle, which travels a
  shorter distance than the wheel.

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Inclined Plane

• A flat surface, set at an upward angle
• It has no moving parts
• Helps overcome larger resistance
• You use relatively little force to push an object
  up a distance.
• The higher the slant the more work is required.

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Pulleys

• Used as a way to use your weight to lift an
  object
• The same amount of force must be used, but the
  direction of the effort force changes

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Pulleys

• Each supporting loop of rope holds half the
  weight, so only half the effort force is need to
  lift an object.

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Work

• Work is done when an object is moved in the
  direction of the applied force.
• The greater the applied force, the more work is
  done.

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Work
Theres Math?!!

• Work force X distance
• Measured in Newtons
• Distance measured in meters
• Joules Newton X meters

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Work

• So try this
• Using a force of 50 N the teacher pushed a
  computer cart across to another classroom 10 m
  away. How much work did the teacher do?
• Wfxd or
• W50Nx10m500J