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