Physical Systems: Simple Machines, Levers, and Gears

Vocabulary flashcards covering simple machines, the three classes of levers, wheels and axles, and gear systems.

Simple Machine

A device that requires a single force to work and is made of only one or two parts (e.g., lever, screw, pulley).

Inclined Plane

A flat, tilted surface (e.g., a ramp); 'plane' means flat surface and 'inclined' means tilted.

Wedge

A modified inclined plane that can be moved back and forth with ease (e.g., axe, door stopper, knife).

Archimedes Screw

A device used in many cultures to lift water; it is an inclined plane that has been cut into a central point.

Lever

A rigid bar that pivots at a fixed point called a fulcrum (e.g., see-saw).

Fulcrum

The pivot point of a lever.

Load Arm

The part of a lever that extends from the fulcrum to the mass being moved.

Effort Arm

The part of a lever that extends from the fulcrum to where the force is applied.

Input Force

The effort force applied to a machine or lever.

Output Force

The force that the lever applies to the load.

Load Force

The force that the input force has to overcome in order to cause movement.

Inclined Plane Family

The category of simple machines that includes the inclined plane, the wedge, and the screw.

Lever Family

The category of simple machines that includes the lever, the wheel and axle, and the pulley.

Class 1 Lever

A lever where the fulcrum is situated between the effort force and the load force (e.g., scissors, pliers, see-saw, prybar).

Class 2 Lever

A lever where the load force is situated between the fulcrum and the effort force (e.g., wheelbarrow, nutcracker).

Class 3 Lever

A lever where the effort force is applied between the fulcrum and the load force (e.g., fishing rod, raking leaves, shooting a hockey puck, lacrosse).

Wheel and Axle

The most common wheel mechanism, consisting of a larger diameter disk (wheel) attached to a smaller diameter shaft (axle).

Advantage of a Larger Diameter Wheel

Allows the user to change a small input force into a larger output force compared to a smaller diameter axle.

Disadvantage of a Larger Diameter Wheel

The driver's hand ends up having to turn farther, which is not ideal.

Gears

A modified wheel and axle, commonly made of plastic or metal, in which the wheel has teeth.

Functions of Gears

Two main purposes: speeding up or slowing down motion, and changing the direction of motion.

Gear Train

A mechanism consisting of two or more wheels with meshed teeth connected together.

Drive Gear

The gear that is turned directly, receiving the input force.

Follower Gear

The gear that turns when the drive gear turns, receiving the output force.

Gear Ratio

The ratio comparing the drive gear to the follower gear based on their circumference or number of teeth.

Gearing Down

A configuration where the drive gear is smaller than the follower gear; makes it easier to lift or pedal a bicycle uphill.

Gearing Up

A configuration where the drive gear is larger than the follower gear; allows the follower gear and wheels to turn quickly, useful when pedaling downhill.