Simple Machines Cheat Sheet

Lever

A rigid bar that pivots on a fixed point (fulcrum) to help lift or move objects.

Example: Seesaw, crowbar, bottle opener

Wheel and Axle

A wheel attached to a central rod (axle) that rotates together to reduce friction when moving objects.

Example: Car wheels, doorknob, steering wheel

Pulley

A grooved wheel with a rope or cable running along the groove. It changes the direction of force and can reduce the amount of force needed.

Example: Flagpole, crane, window blinds

Inclined Plane

A flat surface set at an angle (other than a right angle) to the horizontal. It makes it easier to move objects up or down.

Example: Ramp, slide

Wedge

A triangular-shaped object used to separate, split, or fasten objects.

Example: Axe, knife, doorstop

Screw

An inclined plane wrapped around a cylinder. It is used to fasten objects together or to lift materials.

Example: Jar lid, wood screw

Definition

Mechanical advantage is the ratio of the output force to the input force. It tells you how much a simple machine multiplies your force.

Example: A lever with a mechanical advantage of 2 means you only need to apply half the force to lift an object.

Levers

Mechanical Advantage = Length of Effort Arm / Length of Load Arm

Example: If the effort arm is 4 meters and the load arm is 2 meters, the mechanical advantage is 2.

Inclined Plane

Mechanical Advantage = Length of Slope / Height of Slope

Example: If the slope is 6 meters long and the height is 2 meters, the mechanical advantage is 3.

Wheel and Axle

Mechanical Advantage = Radius of Wheel / Radius of Axle

Example: If the wheel radius is 10 cm and the axle radius is 2 cm, the mechanical advantage is 5.

Work

Work is done when a force moves an object over a distance. Work = Force x Distance

Example: Lifting a 10 N box 2 meters requires 20 Joules of work.

Simple Machines and Work

Simple machines make work easier by reducing the amount of force needed, but they don't reduce the amount of work done. You just apply the force over a longer distance.

Example: Using a ramp to lift a heavy box requires less force than lifting it straight up, but you have to push it a longer distance.

Efficiency

Efficiency is the ratio of useful work output to total work input. No machine is 100% efficient due to friction.

Example: If a machine requires 100 Joules of input work but only produces 80 Joules of useful output work, its efficiency is 80%.