AP Physics 1: Principles of Energy Conservation and Power

System

A defined quantity of matter or region in space chosen for analysis in physics.

Closed System

A system where no mass or energy enters or leaves, maintaining constant total energy.

Open System

A system where energy is transferred in or out, allowing external work to be done.

Work (W)

The energy transferred when a force acts over a distance.

Mechanical Energy (E_mech)

The sum of kinetic and potential energies in a system.

Kinetic Energy (K)

The energy of an object due to its motion, calculated as K = 1/2 mv^2.

Gravitational Potential Energy (U_g)

The energy an object possesses due to its position in a gravitational field, calculated as U_g = mgh.

Elastic Potential Energy (U_s)

The energy stored in a spring when it is compressed or stretched, calculated as U_s = 1/2 kx^2.

Law of Conservation of Energy

Energy cannot be created or destroyed, only transformed from one form to another.

Work by Non-Conservative Forces

Forces that do not conserve mechanical energy, converting it into internal energy.

Power

The rate at which work is done or energy is transferred.

Average Power

Power calculated as work done (or energy changed) divided by the time interval over which the change occurs.

Instantaneous Power

The power at a specific moment, often calculated as P = Fv cos(θ).

Friction

A non-conservative force that opposes motion and converts mechanical energy into thermal energy.

Work-Energy Principle

The change in kinetic energy of an object is equal to the net work done on it.

Dissipation of Energy

The conversion of mechanical energy into heat energy, often due to friction.

Watt (W)

The SI unit of power, equivalent to one joule per second.

Force (F)

An interaction that causes an object to change its velocity, measured in newtons (N).

Velocity (v)

The speed of an object in a given direction.

Change in Mechanical Energy (ΔE_mech)

The change in total mechanical energy as energy is transferred or transformed.

Conservative Forces

Forces that conserve mechanical energy, such as gravitational and spring forces.

Object-Earth System

A system where both kinetic and gravitational potential energy are considered alongside the Earth.

System Boundary Rule

A guideline indicating whether an external force does work on an object or is part of the system.

Scalar Quantity

A physical quantity that has magnitude only, such as work or energy.

Vector Quantity

A physical quantity that has both magnitude and direction, such as force or velocity.

Energy Transfer

The movement of energy from one system or form to another.

Frictional Force (f_k)

A force that opposes the motion of an object, acting in the opposite direction of velocity.