Physics Definitions – Mechanics, Electrostatics & Current Electricity

Vocabulary flashcards covering key definitions in mechanics, electrostatics, and current electricity for exam preparation.

Vector

A physical quantity that has both magnitude and direction (e.g., displacement, velocity, force).

Scalar

A physical quantity that has magnitude only (e.g., distance, speed, mass, time).

Resultant vector

The single vector that has the same effect as two or more vectors acting together.

Distance

The length of the path travelled; a scalar quantity.

Displacement

A change in position of an object; a vector joining initial and final positions.

Speed

The rate of change of distance; a scalar quantity (speed = distance ÷ time).

Velocity

The rate of change of displacement; a vector quantity (v = Δs / Δt).

Acceleration

The rate of change of velocity (a = Δv / Δt).

Weight (Fg)

The gravitational force the Earth exerts on any object on or near its surface (Fg = m g).

Normal force

The perpendicular force exerted by a surface on an object in contact with it.

Frictional force

The force that opposes the motion of an object and acts parallel to the contact surface.

Newton’s first law

An object remains at rest or in uniform motion unless acted on by a net (resultant) force.

Inertia

The property of an object that causes it to resist changes in its state of rest or uniform motion.

Newton’s second law

When a net force acts on mass m, the object accelerates in the direction of the net force (a ∝ Fnet and a ∝ 1/m, a = Fnet / m).

Newton’s third law

If object A exerts a force on object B, object B simultaneously exerts an equal-magnitude force in the opposite direction on object A.

Coulomb’s law

The force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of their separation distance.

Electric field

A region of space in which an electric charge experiences a force.

Electric field at a point

The force per unit positive charge at that point (E = F / q).

Potential difference (V)

The work done per unit positive charge (V = W / q).

Current (I)

The rate of flow of charge (I = q / t).

Ohm’s law

For a conductor at constant temperature, current is directly proportional to the potential difference across it.

Resistance (R)

A material’s opposition to the flow of electric current.

Electromotive force (emf)

The total energy supplied per coulomb of charge by a cell or source.