Simple Machine Matching

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Simple Machine Matching
1st Class Lever
2nd Class Lever
Slide
Hockey Stick
3rd Class Lever
Inclined Plane
Axe
Pulley
Door knob
Nutcracker
Screw
Crane
Wedge
Wheel and Axle
Hand Brakes
Drill
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Types of Machines
Chapter 4 Section 3
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Levers

• A lever is a simple machine consisting of a bar
  that pivots at a fixed point, called a fulcrum.
• Levers are used to apply a force to a load.
• There are 3 classes of lever, based on the
  location of the fulcrum, the load, and the input
  force
• First, Second, and Third Class

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First Class Levers

• The fulcrum is between the input force and the
  load.
• Depending on the location of the fulcrum, they
  can be used to increase force or to increase
  distance.

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The fulcrum is closer to the load than the input
force, so the mechanical advantage is greater
than one. The output force is increased because
it is exerted over a shorter distance.
The fulcrum is exactly in the middle, so the
mechanical advantage is one. The output force is
not increased because the input forces distance
is not increased.
The fulcrum is closer to the input force than to
the load, so the mechanical advantage is less
than one. Although the output force is less than
the input force, a gain in distance occurs.
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Second Class Levers

• The load is between the fulcrum and the input
  force.
• They do not change the direction of the input
  force, but they allow you to apply less force
  than the force exerted by the load.
• Because the output force is greater than the
  input force, you must exert the input force over
  a greater distance.

Output force
Input force
load
fulcrum
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Using a 2nd class lever results in a mechanical
advantage that is greater than one. The closer
the load is to the fulcrum, the more the force is
increased and the greater mechanical advantage.
Mechanical advantage output force input
force
Input force
Output force
fulcrum
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Third Class Levers

• The input force is between the fulcrum and the
  load.
• They do not change the direction of the input
  force and they do not increase the input force.
• The output force is always less than the input
  force.

Output force
Input force
load
fulcrum
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Using a 3rd class lever results in a mechanical
advantage of less than one because force is
decreased. But, they are helpful because they
increase the distance through which the output
force is exerted.
Input force
Mechanical advantage output force input
force
Output force
fulcrum
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Inclined Planes

• An inclined plane is a simple machine that is a
  straight, slanted surface.
• It allows you to apply a smaller force over a
  greater distance.

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Mechanical Advantage of Inclined Planes
MA 3 m 5 0.6 m
The longer the inclined plane is compared to the
height, the greater the mechanical advantage.
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Inclined Plane
Input force
Output force
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Wedges

• A wedge is a double inclined plane that moves.
• It applies an output force that is greater than
  your input force, but you apply the input force
  over a greater distance.
• The greater the distance you move the wedge, the
  greater the force it applies on the object.

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Mechanical Advantage of Wedges
MA 8 m 4 2 m
2 m
8 m
1 m
10 m
The longer and thinner the wedge is, the greater
the mechanical advantage.
MA 10 m 10 1 m
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Wedge
Input force
Output force
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Screws

• A screw is an inclined plane that is wrapped in a
  spiral.
• When rotated, a small input force is applied over
  the long distance along the inclined plane (by
  you) AND the screw applies a large output force
  through the short distance it is pushed.

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Mechanical Advantage of Screws

• If you could unwind the inclined plane of a
  screw, you would see that it is very long and has
  a gentle slope.
• The longer the inclined plane is compared to the
  height, the greater the mechanical advantage.

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Screw
Input force
Output force
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Wheel and Axle

• A wheel and axle is a simple machine consisting
  of two circular objects of different sizes.

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How a wheel and Axle works
1) When a small input force is applied to the
wheel, it rotates through a circular distance.
Input force
2) As the wheel turns, so does the axle. But
because the axle is smaller than the wheel, it
rotates through a smaller distance, which makes
the output force larger than the input force.
wheel
axle
Input force
Output force
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Mechanical Advantage of a Wheel and Axle
Radius of axle 3 cm
Radius of wheel15 cm
MA 15 cm 5 3 cm
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Pulleys

• A pulley is a simple machine consisting of a
  grooved wheel that holds a rope or a cable.
• A load is attached to one end of the rope, and an
  input force is applied to the other end.
• There are two kinds of pulleys
• Fixed and moveable

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Fixed Pulleys

• A pulley that only changes the direction of a
  force. They do not increase the force.
• They are attached to something that does not move.

A fixed pulley only spins. So the distance
through which the input force and output force
are exerted are the same. So the mechanical
advantage is one.
Input force
Output force
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Moveable Pulleys

• They are attached to the object being moved and
  they do not change a forces direction.

A movable pulley moves up with the load as it is
lifted. The output force is multiplied because
the combined input force is exerted over twice
the distance of the output force.
Input force
Output force
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Block and Tackle

• A fixed and movable pulley are used together.
  Where are they?
• The more pulleys that are used, the greater the
  mechanical advantage.

The mechanical advantage of this block and tackle
is 4 because there are 4 rope segments that
support the load. This multiplies your input
force 4 times, but you have to pull the rope 4 m
just to lift the load 1 m.
Input force
Output force
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Compound Machines

• Compound machines are machines that are made of
  two or more simple machines. Where are the simple
  machines?

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Mechanical Efficiency of Compound Machines

• The more moving parts, the less mechanical
  efficiency. WHY?
• How can we help improve the efficiency?