1. LEVERS ~ Archimedes

2. Introducing… The Lever A lever includes a stiff structure (the lever) that rotates around a fixed point called the fulcrum. fulcrum

3. 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 (measured from the fulcrum to the point at which the force is applied) Resistance Arm – The part of the lever that applies the resistance force (measured from the fulcrum to the center of the resistance force)

6. Anatomy of the lever Fulcrum – point around which the lever rotates Input Force – Force exerted ON the lever Output Force – Force exerted BY the lever

7. Levers and the human body Your body contains muscles attached to bones in ways that act as levers. Here the biceps muscle attached in front of the elbow opposes the muscles in the forearm. Can you think of other muscle levers in your body?

8. By using the length of the effort arm and the resistance arm you can find the ideal mechanical advantage. –Ideal Mechanical Advantage (IMA) – 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 resist arm l r

9. Teachertube Video

10. Three Classes of Levers First Class - fulcrum between Input and output  Second Class – output between fulcrum and input  Third Class – input between fulcrum and output

11. First Class Levers – “See-Saw” Levers 1 st Class Lever - The fulcrum is located between the effort arm and the resistance arm. First class levers can multiply force and distance. –Examples: scissors, see-saw, hammer’s claws, pliers, etc…

12. 2 nd Class Levers – “Wheelbarrow Levers” 2 nd Class Lever - resistance is located between the effort arm and the fulcrum. These levers multiply the force but the direction stays the same. –Example: wheelbarrow, stapler, bottle opener, finger nail clippers, nut cracker

13. 3 rd Class Lever - 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, broom, shovel, fishing pole, tweezers, tongs 3 rd Class Levers - “Tweezers”