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Home , Scraper (archaeology), Wheel

Simple 14.2 Bill Nye- Simple Machines

• https://www.youtube.com/watch?v=A8mCYA XUPgA • 25 mins Levers • Solid bar that rotates or turns around fixed fulcrum • Can multiply force or change direction

3 Classes of Levers

• 1st Class- fulcrum b/w input and output force – Changes direction & size of force • Ex. Crowbar 3 Classes of Levers

• 2nd class- output between input and fulcrum – Increases output force • Ex. Bottle opener, barrow 3 Classes of Levers

• 3rd class- input between output and fulcrum – Reduces distance of input force or increases speed of end of lever

Wheel &

• Wheel attached to shaft/axel • Acts like rotating collection of levers (axel at wheel’s center acts as fulcrum) • Ex. Screw drivers, wheel, doorknobs, electric fans – Turn wheel  turns axel (smaller) output force acts over shorter distance (door knob, ) – Turn axel wheel (larger) force acts over larger distance (ex. & of )

• Wheel w. grooved & or cable rides in groove – Attached = fixed pulley • Makes easier by changing direction of force • Must apply enough force to overcome weight of object & • Same distance pulled as lifted. – Movable pulley setup : one end of rope is fixed but wheel can move • Person pulling rope provides output force • Does not change direction of force but multiplies force • But must pull 2x far – Block & tackle • Combo fixed & movable- pulley system • Can use more rope sections to support weight of object, decreases force needed to lift

Inclined Plane

• Sloped surface, ramp • makes work easier b/c ramp supports part of weight whole move f/ one level to another (ramp applies force on object, counteracting Gravity ) • Only need enough force to overcome smaller net force that pulls object down parallel to incline • less steep inclined plane, less force needed, but further must travel Wedge

• Thick and thin edged object • Used to cut, split or pierce objects (sometimes hold things together) • Type of inclined plane but not always stationary • Ex. Door stop, chisel, ice , / (2 sided plane) • Angle of cutting edge determines how easily can cut through object – Thin wedge- small angles- less input force – Ex. Sharp knife better than dull one • Smaller edge = smaller surface area for input force, increases pressure = easier to break through surface

Screw

• Inclined plane wrapped around cylinder or cone to form spiral • Used to raise/lower weights and fasten objects • Ex. Drills, jar lids, screw clamps, nuts & bolts • If threads closer together, force must be applied over greater distance but less force • Better than nail b/c friction

Ideal Mechanical Advantage

• Recall: mechanical advantage is how many times a multiplies input force & = Fout/Fin • If less force, greater distance • Ideal Mechanical advantage: mechanical advantage calculated when assume 100% efficiency (no work lost to friction) IMA of Simple Machines • Inclined plane: 푙푒푛푔푡ℎ 표푓 𝑖푛푐푙𝑖푛푒 푙 – 퐼푀퐴 = = ℎ푒𝑖푔ℎ푡 표푓 𝑖푛푐푙𝑖푛푒 ℎ • Wheel & axel: 푟푎푑𝑖푢푠 표푓 𝑖푛푝푢푡 • 퐼푀퐴 = 푟푎푑𝑖푢푠 표푓 표푢푡푝푢푡 • Ex. (input > output so IMA < 1) • Ex. Steering wheel (input less than output so IMA > 1) • Lever: 푑𝑖푠푡푎푛푐푒 푓푟표푚 𝑖푛푝푢푡 푡표푓푢푙푐푟푢푚 푑𝑖푛 • 퐼푀퐴 = = 푑𝑖푠푡푎푛푐푒 푓푟표푚 표푢푡푝푢푡 푡표 푓푢푙푐푟푢푚 푑표푢푡 • applies to all 3 classes of levers