circumference

Velocity describes how fast an object moves in a specific direction. It is a technical word for speed used often in science and math.

Momentum is the power that a moving object has to keep moving. It depends on how heavy the object is and how fast it is going. It is also used to describe a plan or project that is growing and becoming more successful.

Magnetism is a physical force that pulls certain metals toward each other or pushes them away. It is also used to describe a special charm that attracts people to a person.

Radiation is energy that travels through space as waves or very small particles. It comes from natural sources like the sun and from machines like X-rays in hospitals.

Wavelength is the distance between two peaks of a light or sound wave. It is also used to describe when people have the same ideas and understand each other.

Optics is the branch of science that studies light and how it interacts with things like lenses and mirrors. In modern usage, it also refers to how an event or action is seen by the public.

Thermodynamics is the study of heat and how it moves. It explains how energy changes from one form to another, such as how heat can turn into movement.

An atom is the smallest possible part of a chemical element. Everything in the world is made of millions of these very tiny particles.

A reaction is a response to an action or a situation. In science, it is what happens when two or more substances are mixed together to create a change.

A solution is a liquid mixture where a solid or gas is fully mixed into a liquid. It also means the correct answer to a problem or a difficult puzzle.