Grade 8 Mechanical Systems

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Grade 8 Mechanical Systems

• Topic 1 Mechanical Advantage

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What is Mechanical Advantage?

• Mechanical advantage is the comparison of the
  force produced by a machine to the force applied
  to the machine.
• In other words, mechanical advantage is the
  comparison of the size of the load to the size of
  the effort force.

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What is Mechanical Advantage?

• The smaller the effort force compared to the
  load, the greater the mechanical advantage.

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What is Mechanical Advantage?

• The formula for Mechanical Advantage is
• MA Load Force(LF) LF Effort Force
  (EF) EF
• No units are used to express mechanical advantage
  because it is a ratio. (The units cancel out).

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What is Mechanical Advantage?

• If a branch lever has exerted a force 5 times
  greater than the force you exerted on it, what
  does that mean? The lever makes the job 5 times
  easier. (It takes only 1/5 of the unaided effort
  to lift the car.)

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What is Mechanical Advantage?

• Machines can have a mechanical advantage that is
  greater than 1 or less than 1 or equal to 1.

MA gt 1
MA lt 1
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What is Mechanical Advantage?

• Some machines do not have any effect on the
  effort force that you exert. They simply change
  the direction of the effort force.

100 N
100 N
MA 1
MA 1
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Another Way to Calculate MA

• The concepts of mechanical advantage and work can
  be linked.
• The closer you are to the fulcrum, the harder it
  is to lift an object. The longer the effort arm,
  the less effort it will take to lift an object.

MA 1
MA 5
MA 1/5
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Another Way to Calculate MA

• Another formula that can be used to calculate the
  mechanical advantage of lever is
• MA Effort Arm (EA) Load Force (FL)
• Load Arm (LA) Effort Force (FE)

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Another Way to Calculate MA

• An application of levers is keyhole surgery
  wherein a long tube is pushed through the
  incision to the part of the patients body
  requiring surgery. Electronically controlled
  levers cut and sew as needed while the surgeon
  watches on a TV screen.

Laparoscopic surgery
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Another Way to Calculate MA

• An example where you might want to increase the
  force that you yourself exert would be using
  tweezers for delicate precision work.

Tweezers can be used to pick up small, delicate
items that can be broken or damaged if too much
force is applied.
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Speedy Levers

• The advantage of a class 3 lever is that the
  force will move the load a greater distance and
  at a faster speed.
• Speed is the rate of motion (how fast something
  moves) or the rate at which something changes
  position. It is defined as distance over time.

Speed distance time
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Speedy Levers

• Most of the levers inside your body have a
  mechanical advantage smaller than one.

Because of these levers, humans are capable of
precision work as well as speed and quick
reflexes.
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Machines Made to Measure

• Some of the factors taken into account when
  designing products for people are fit, comfort,
  function, design (shape), ease, cost.
• Ergonomics is science of designing machines.

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Machines Made to Measure

• Ergonomics is especially important in the design
  of work environments where occupational safety is
  an issue.

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Machines Made to Measure

• Carpal Tunnel Syndrome is a common problem for
  people who type a lot. It causes numbness and
  pain in the joints.

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Machines Made to Measure

• A person can prevent or treat Carpal Tunnel
  Syndrome by using other machines that put less
  stress on fingers.

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Review

• The two formulas for mechanical advantage are
• MA Effort Arm (EA) or Load Force (LF)
• Load Arm (LA) Effort Force (EF)

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Review

• A person may choose to use a machine with a
  mechanical advantage of 1 because it can change
  the direction of the effort (e.g. a class 1
  lever).

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