Welcome Back Minions!!! Warm up on the board…
Opener for Levers and Screws Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. -Archimedes (btw… the lever would have to be around 100,000,000,000,000,000,000,000 meters long and moved 100,000,000,000,000,000,000 meters down just to budge the Earth about 1mm!!!!!)
Levers Where have you seen levers before? So what is a lever? • Lever • A rigid bar that is free to pivot, or rotate, on a fixed point.
Parts of a Lever • Fulcrum • Fixed point that a lever pivots around • Input Force • The force exerted to the machine • Output Force • The force exerted from the machine to the object it acts upon
Power of 3… • 3 Classes of Levers • First Class Levers • Second Class Levers • Third Class Levers • All depends on the fulcrum!
First Class Lever • First Class Lever • Always changes the direction of the force. • Fulcrum closer to output force; the lever increases force. • Fulcrum closer to input force; the lever increases distance.
Give me examples… • First Class Levers • Seesaws • crowbar • scissors • an oar attached to a boat • a claw hammer • trebuchet siege weapon
Second Class Lever • Second Class Lever • Increase force but do not change the direction of the force.
Give me examples… • Second Class Lever • wheel barrow • hole puncher • Stapler • nutcracker • bottle opener • nail clippers • paper cutter
Third Class Lever • Third Class Lever • Increases distance, but do not change the direction of the force.
Give me examples… • Third Class Lever • Baseball bat • Broom • Doors • Fishing rod • Tweezers • Mouse trap • Catapult
Lever – Mechanical Advantage • Mechanical Advantage • Increases input force • Change direction of Input force
Screw Where have you seen screws before? What is a screw? • Screw • Inclined plane wrapped around a cylinder
Screw • How it works… • Input force = You turning the screw • Output force = thread’s force on object • Friction holds it in place
Screw • A Paper Screw • Paper & Pencil
Screw • Mechanical Advantage • Closer the threads are together (the pitch), the greater the advantage. • Has to turn more times to secure the screw.
Examples… • Examples of a Screw • brace and bits • screw lid jar • swivel piano stool • meat grinder • drills • door lock • Submarine hatch • machine screws • wooden handled cork screw
Finally… • Archimedes Screw • Move water to irrigate crops • Move water from polders