Simple Machines

Simple Machines

There are six simple machines: The lever The wheel and axel The inclined plane The wedge The screw The pulley

Levers

Lever- a rigid bar that is free to move around a fixed point.

Ex. Screwdriver to open a paint can lid. The fixed point the bar rotates around

is the fulcrum Levers are classified into three

categories based on the locations of : The input force The output force The fulcrum

Levers

The input arm of a lever is the distance between the input force and the fulcrum

The output arm is the distance between the output force and the fulcrum

To calculate the IMA of any lever: Divide the input arm by the

output arm.Input arm

Output arm

First-Class Levers

The position of the fulcrum identifies a first-class lever. The fulcrum is always located

between input force and the out put force

Depending on location of fulcrum, the mechanical advantage can be greater, equal, or less than 1.

Ex. Seesaw, scissors, tongs, screwdriver

Second-Class Levers

A lever is considered second-class, if the output force is located between the input force and the fulcrum. Ex. Wheelbarrow Mechanical advantage is always

greater than 1

Third-Class Lever

The input force is located between the fulcrum and the output force.

The output distance over which the third-class lever exerts its force is always larger than the input distance you move the lever through.

The mechanical advantage is always less than 1. Ex. Baseball bats, hockey sticks, and

golf clubs

Wheel and Axle

A wheel and axle is a simple machine that consists of two disks or cylinders, each one with a different radius. Ex. Steering Wheel To calculate the IMA, divide the radius

where the input force is exerted by the radius where the output force is exerted.

Incline Planes

An incline plane is a slanted surface along which a force moves an object to a different elevation.

The IMA is the distance along the incline plane divided by its change in height. Ex. A 6meter long ramp that gains 1

meter of height has an IMA of 6

Wedges and Screws

Similar to incline planes but have a sloping moving surfaces. Wedge is a V-shape object whose

sides are two inclined planes sloped toward each other.

A thin wedge of a given length has a greater IMA than a thick wedge of the same length.

Ex. Knife blade

Wedges and Screws

A Screw, is an incline plane wrapped around a cylinder.

Screws with threads that are closer together have a greater IMA

Pulleys

A pulley is a simple machine that consists of a rope that fits into a groove in a wheel.

Pulleys produce an output force that is different in size, direction, or both, from that of the input force.

IMA is equal to the number of rope sections supporting the load being lifted. Three types of pulleys

Fixed- changes only the direction of the input force

Movable- changes both the direction and the size of the input force

System- are made up of both fixed and movable pulleys