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Simple Machines and Mechanical Advantage

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Title: Simple Machines and Mechanical Advantage


1
Simple Machines and Mechanical Advantage
2
Simple Machines
  • Ancient people invented simple machines that
    would help them overcome resistive forces and
    allow them to do the desired work against those
    forces.

3
Simple Machines
  • The six simple machines are
  • Lever
  • Wheel and Axle
  • Pulley
  • Inclined Plane
  • Wedge
  • Screw

4
Simple Machines
  • A machine is a device that helps make work easier
    to perform by accomplishing one or more of the
    following functions
  • transferring a force from one place to another,
  • changing the direction of a force,
  • increasing the magnitude of a force, or
  • increasing the distance or speed of a force.

5
Mechanical Advantage
  • It is useful to think about a machine in terms of
    the input force (the force you apply) and the
    output force (force which is applied to the
    task).
  • When a machine takes a small input force and
    increases the magnitude of the output force, a
    mechanical advantage has been produced.

6
Mechanical Advantage
  • Mechanical advantage is the ratio of output force
    divided by input force. If the output force is
    bigger than the input force, a machine has a
    mechanical advantage greater than one.
  • If a machine increases an input force of 10
    pounds to an output force of 100 pounds, the
    machine has a mechanical advantage (MA) of 10.
  • In machines that increase distance instead of
    force, the MA is the ratio of the output distance
    and input distance.
  • MA output/input

7
  • No machine can increase both the magnitude and
    the distance of a force at the same time.

8
The 6 Simple Machines
Wedge
Screw
Inclined Plane
Pulley
Wheel and Axle
Lever
9
Inclined Plane
10
Inclined Plane
  • The Egyptians used simple machines to build the
    pyramids. One method was to build a very long
    incline out of dirt that rose upward to the top
    of the pyramid very gently. The blocks of stone
    were placed on large logs (another type of simple
    machine - the wheel and axle) and pushed slowly
    up the long, gentle inclined plane to the top of
    the pyramid.

11
Inclined Planes
  • An inclined plane is a flat surface that is
    higher on one end
  • Inclined planes make the work of moving things
    easier

12
The Lever
  • A lever is a rigid bar that rotates around a
    fixed point called the fulcrum.
  • The bar may be either straight or curved.
  • In use, a lever has both an effort (or applied)
    force and a load (resistant force).

13
There are 3 Classes of Levers
  • Depends on the location of 3 items
  • 1. Fulcrum fixed point on a lever
  • 2. Effort Arm the part of the lever that
    exerts the effort force.
  • 3. Resistance Arm the part of the lever that
    exerts the resistance force.

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14
1st Class Lever
  • Changes the direction of the force
  • Multiplies effort force
  • Magnifies speed and distance
  • Ex seesaw, crowbar, scissors

15
2nd Class Lever
  • Multiply effort force
  • Mechanical advantage is always greater than 1.
  • Ex bottle opener, boat oars, wheel barrow

16
3rd Class Lever
  • Magnifies speed and distance
  • Mechanical Advantage always less than 1
  • Ex baseball bat, golf club, broom, shovel

17
WHEEL AND AXEL
  • The axle is stuck rigidly to a large wheel. Fan
    blades are attached to the wheel. When the axel
    turns, the fan blades spin.

18
Pulleys
  • Pulley are wheels and axles with a groove around
    the outside
  • A pulley needs a rope, chain or belt around the
    groove to make it do work

19
Diagrams of Pulleys
  • Fixed pulley

A fixed pulley changes the direction of a force
however, it does not create a mechanical
advantage.
Movable Pulley
The mechanical advantage of a moveable pulley is
equal to the number of ropes that support the
moveable pulley.
20
COMBINED PULLEY
  • The effort needed to lift the load is less than
    half the weight of the load.
  • The main disadvantage is it travels a very long
    distance. 

21
Mechanical Advantage
  • Ratio of Output Force to Input Force
  • Follows simple pattern with Ropes and Pulley
    system

22
Rube Goldberg Machines
  • Rube Goldberg machines are examples of complex
    machines.
  • All complex machines are made up of combinations
    of simple machines.
  • Rube Goldberg machines are usually a complicated
    combination of simple machines.
  • By studying the components of Rube Goldberg
    machines, we learn more about simple machines
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