A push or pull that can cause motion, or cause an object to change it's motion.

​​Force

The process of moving or changing position.

​​Motion

When one force is stronger than another, the result is motion.

​​Unbalanced force

A force that resists motion (when one object rubs against another). Friction causes things to stop or slow down.

​​Friction

A force that attracts things to earth. Mass and distance determines the strength of gravity.

Gravity

is the frictional force of air. As an object moves, air resistance slows it down. The faster an object moves, the greater the resistance.

Air resistance

A long and stable body that rests on a fulcrum (support). The fulcrum is the point where the lever pivots.
wheelbarrow, shovel, see-saw, crowbar, arms and legs

Lever

Made with a looping rope over one or more wheels, used to lift heavy objects. When you pull on one rope, it creates an upward pull on the other end. Elevators are examples.

Pulley

A wheel with a rod attached in the middle as an axle to help life or move loads. Doorknobs, screwdriver, steering wheel are examples.

Wheel and axle

An inclined plane is a flat surface with one end higher than the other. It allows heavy objects to slide up to a higher point rather than be lifted. stairs, slides, ramps

Inclined plane

Screw

A special kind of inclined plane that is wrapped around a pole. This is used to lift things and hold them together. Examples are swivel jars, jar lids and screws.

Wedge

Two inclined planes back to back. It is used to push two objects apart. Examples: knives, axes, doorstops, chisels.