Conservation Laws in Physics to Know for AP Physics C: Mechanics (2025)

Conservation of Energy

States that energy cannot be created or destroyed, but only converted from one form to another within a closed system.

Closed System

A physical system that does not exchange matter with its surroundings.

Kinetic Energy

The energy an object possesses due to its motion.

Potential Energy

The energy stored in an object due to its position or state.

Work-Energy Theorem

The principle stating that the work done on an object equals the change in its kinetic energy.

Inelastic Collisions

Collisions in which kinetic energy is not conserved, but total energy is.

Conservation of Linear Momentum

States that the total momentum in an isolated system remains constant if no external forces are acting.

Momentum

The product of an object's mass and velocity.

Elastic Collisions

Collisions where both momentum and kinetic energy are conserved.

Impulse

The change in momentum which results from a force applied over time.

Conservation of Angular Momentum

States that if no external torque acts on a system, the total angular momentum remains constant.

Angular Momentum

The rotational equivalent of linear momentum, dependent on moment of inertia and angular velocity.

Figure Skater

An example of conservation of angular momentum, wherein a skater pulls their arms in to spin faster.

Conservation of Mass

States that mass cannot be created or destroyed in a closed system.

Chemical Reactions

Processes where mass is converted but not created or destroyed.

Mass-Energy Equivalence

The principle that mass can be converted to energy and vice versa, expressed in Einstein's equation E=MC².

Conservation of Electric Charge

States that the total electric charge in an isolated system remains constant over time.

Electric Charge

A fundamental property of matter that causes it to experience a force in an electric field.

Kirchhoff's Current Law

States that the total current entering a junction equals the total current leaving the junction.

Lightning

A natural phenomenon resulting from the redistribution of electric charge between clouds and the Earth.

Electrochemical Reactions

Reactions in which charge is transferred between electrodes yet total charge conservation is maintained.

Universal Application

Conservation laws apply universally across different scales, from subatomic particles to astronomical systems.

Simplification of Complex Problems

Conservation principles allow for easier problem solving without tracking every force or interaction.

Interdisciplinary Connections

These laws link various branches of physics, highlighting a unified framework for understanding physical phenomena.

Energy Conversion

The process of transforming energy from one form to another (e.g., kinetic to potential).

Thermodynamics

The branch of physics that deals with heat, work, and energy.

Astrophysics

The branch of astronomy concerned with the physical properties and behavior of celestial bodies.

Electromagnetism

The branch of physics involving the study of electric charge and its interactions.

Quantum Physics

The study of physics at the smallest scales of energy levels of atoms and subatomic particles.

Roller Coasters

Systems that rely on energy conversion between kinetic and potential energy during rides.

Pendulum

An object that swings back and forth, demonstrating energy conversion between potential and kinetic energy.

Rocket Launch

An example of momentum conservation where expelled gases produce forward motion.

Gun Recoil

The backward motion of a gun when it's fired, illustrating conservation of momentum.