Physics equations and formulas

Physics expresses its laws as mathematical equations that relate measurable quantities to one another. Mastering a field largely means understanding which formula applies to a situation, what each symbol stands for, and how the relations are derived. The equations span classical mechanics through the modern physics of the twentieth century, and most carry a small number of physical constants that fix the scale of the effect they describe.

Mechanics provides the starting point. Newton's laws of motion connect force, mass and acceleration, and lead to equations for momentum, energy and the motion of objects under gravity. The work-energy and conservation laws let problems be solved without tracking every force in detail. Thermodynamics adds relations among heat, temperature, pressure and volume, including the gas laws and the principles of energy conservation and entropy. Electromagnetism describes electric and magnetic fields, the forces they exert on charges, and how changing fields produce one another, summarised in compact form by Maxwell's equations.

Optics contributes its own well-known formulas. The thin-lens and mirror equations relate object distance, image distance and focal length, and predict whether an image is real or virtual, magnified or reduced. Modern physics extends the classical picture: special relativity links energy and mass, and quantum relations connect a particle's energy to the frequency of associated radiation. Across all these areas, formula collections serve as a reference for the constants, units and standard forms needed to set up and check calculations in study and engineering work.

Frequently asked questions

What does Newton's second law state?

It states that the acceleration of an object is proportional to the net force acting on it and inversely proportional to its mass, usually written as force equals mass times acceleration.

What is the thin-lens equation used for?

It relates the focal length of a lens to the object and image distances, allowing the position and nature of an image formed by a lens to be calculated.

What is meant by modern physics?

Modern physics refers to developments from about 1900 onward, chiefly relativity and quantum theory, which describe behaviour at very high speeds and at atomic scales.