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# 2008lever

## on Apr 16, 2009

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## 2008leverPresentation Transcript

• Notes: Levers
• CW: Levers
• H: Types of Levers
• Levers April 17, 2009
• ~ Archimedes Give me a place to stand and I will move the Earth.
• Objectives
• Analyze and label the parts of a lever
• Provide examples of first, second and third class levers.
• Calculate and determine the mechanical advantage of a lever.
• Forces in Machines
• A simple machine is an unpowered mechanical device, such as a lever .
• A bar that is free to move about a fixed point
• Parts of a lever
• Fulcrum – The fixed point of a lever
• Effort Arm – The part of the lever that the effort force is applied to
• Resistance Arm – The part of the lever that applies the resistance force
Anatomy of the lever
• Input Force – Force exerted ON the lever
• Output Force – Force exerted BY the lever
Forces
• What the mechanical advantage of a machine would be if there were no energy lost due to friction
• IMA= length of effort arm = l e . length of resistance arm l r
• There are 3 types of levers
• 1 st Class Levers
• 2 nd Class Levers
• 3 rd Class Levers
• 1 st Class Lever
• The fulcrum is located between the F e and the F r . First class levers can multiply force and distance.
• Examples: Scissors, see-saw
•
• 2 nd Class Lever
• The resistance is located between the effort force and the fulcrum. These levers multiply the force but the direction stays the same.
• Example: Wheelbarrow
• The effort force is located between the fulcrum and the resistance. The effort arm is always shorter than the resistance arm so it cannot multiply the force and the MA is always less than 1.
• Examples: Rake, hockey stick
3rd Class Lever