How Tools Work

The Six Simple Machines

Lever

Inclined Plane

Wedge

Screw

Pulley

Wheel and Axle

Lever

A bar that pivots on a fulcrum—a fixed point

Levers apply force to a load

Three classes, depending on placement of fulcrum, load, and input force

                                                

Inclined Plane

A straight, slanted surface Ex: a ramp

Requires less input force than going straight up

***does NOT reduce work (W= f x d)

Wedge Two inclined planes

that move Often used for

cutting You a knife down as

it cuts apart

The sharper the wedge, the greater output force for your input force

Screw An inclined plane

wrapped in a spiral around a cylinder Usually used as

fasteners

Smaller force over a longer distance The small force of

you turning pushes the screw along its spiraled threads

Pulley A grooved wheel

that holds a rope or cable

A load is attached to one end of the rope, and the input force is applied to the other end

Wheel and Axle Two circular objects of

different sizes used to create a larger output force

Turn the larger circle around a longer distance as the smaller circle, traveling a shorter distance, creates a larger output force

The larger the wheel, the less force needed to move the load

Compound Machines

A machine made up of two or more simple machines

Most machines in the world, including how your body works, are compound

Mechanical Advantage How many times a

machine multiplies force

Mechanical Advantage is calculated by dividing the output force by the input force MA= out/in

If MA > 1, the machine helps lift heavy objects

If MA < 1, the machine increases the distance and reduces the output force

Name that Machine!