Levers

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Levers
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Key Terms

• Force A force is a push or a pull on an object
• Work When force causes an object to move
• Machine a device that allows you to do work
  that is easier or more effective
• Lever rigid object that rotates around a fixed
  point

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• Mechanical advantage a measure of how much
  easier it is to do work using a machine
• Fulcrum fixed point that a lever rotates
  around
• Effort force force that you apply on a lever
• Resistance force force that a lever exerts on
  an object

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Classification of a Lever

• A lever is classified by the location of the
  fulcrum relative to the effort force and the
  resistance force.
• First class fulcrum is between the effort force
  and the resistance force
• Second class resistance force is between the
  effort and the fulcrum
• Third class the effort force is between the
  resistance force and the fulcrum

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Types of levers

• First Class lever
• Always change the direction of the effort force

Resistance force
Effort force
Fulcrum
Examples scissors, seesaws, taking a nail out
of a board
Body example Top of neck and head tilting back
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• Second class lever
• Increase force, but do not change the direction
  of the effort force.

Effort force
Resistance force
Fulcrum
Example wheel barrel, bottle opener
Body example Ball of foot-fulcrum, effort
force muscle in calf, and resistance force used
to raise your body
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• Third Class lever
• These levers increase distance but do not change
  the direction of the force

Effort force
Resistance force
Fulcrum
Examples shovel, rakes, baseball bats
Body example Elbow is fulcrum, bicep is effort
force, resistance force lifts arm up.
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What is what?

• Muscles provide the force
• Bones act as levers
• Joints act as fulcrums