Mind the Gap Physics – Vocabulary Flashcards (English)

Key vocabulary terms and concise definitions drawn from the Mind the Gap physics notes, covering Mechanics, Momentum, Energy, Waves, Optics, Electrostatics, Circuits, Electrodynamics, and Spectra.

vector

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

scalar

A quantity that has magnitude only, with no direction (e.g., speed, distance).

mass

A measure of the amount of matter in an object; determines inertia and is constant.

weight

The gravitational force pulling on a mass, equal to m g; a vector.

gravity (g)

Acceleration due to gravity, approximately 9.8 m/s^2 on Earth.

normal force

The force perpendicular to a contact surface exerted by a surface on an object.

friction

Resistive force that opposes motion between contacting surfaces; includes static and kinetic friction.

coefficient of friction (μ)

A value that depends on the materials in contact, used to calculate friction forces (μs for static, μk for kinetic).

resultant (net) force

The vector sum of all forces acting on an object.

Newton’s First Law (Law of Inertia)

An object at rest stays at rest and an object in motion stays in motion unless acted on by a non-zero net external force.

Newton’s Second Law

Fnet = m a; the acceleration is proportional to net force and inversely proportional to mass.

Newton’s Third Law

For every action, there is an equal and opposite reaction; forces come in pairs on different objects.

Newton’s Law of Universal Gravitation

Fg ∝ m1 m2 / r^2; the gravitational force between two masses decreases with distance.

mass

Amount of substance; a scalar quantity that determines inertia.

momentum (p)

p = m v; a vector quantity describing motion, conserved in closed systems.

impulse

J = F Δt; the change in momentum when a force acts over a time interval.

conservation of linear momentum

In a closed system, total momentum remains constant.

elastic collision

Collisions where momentum is conserved and kinetic energy is conserved.

inelastic collision

Collisions where momentum is conserved but kinetic energy is not fully conserved.

free fall

Motion under gravity with negligible air resistance.

g (gravitational acceleration)

Acceleration due to gravity; direction is downward toward Earth.

projectile

An object moving under the influence of gravity (and possibly other forces) with a curved trajectory.

displacement

The straight-line distance and direction from the starting point to the ending point.

velocity

Rate of change of displacement; a vector quantity.

speed

Rate of motion; magnitude of velocity; scalar.

vertical projectile motion

Motion of a projectile in a vertical plane; often analyzed with separate vertical and horizontal components.

work

Scalar quantity equal to F Δx cos θ; the transfer of energy by force.

energy

The capacity to do work; has several forms (kinetic, potential, etc.).

kinetic energy (Ek)

Ek = 1/2 m v^2; energy of motion.

potential energy (Ep)

Energy due to position, e.g., Ep = m g h (gravitational potential energy).

conservation of energy

In a closed system, mechanical energy remains constant (sum of Ek and Ep).

power

Rate of doing work; P = W/Δt or P = F v (work per time).

conservative force

Work done between two points is path independent (e.g., gravity, spring).

non-conservative force

Work depends on the path (e.g., friction, air resistance, tension).

Doppler effect

Change in observed frequency due to relative motion of source and observer.

frequency (f)

Number of cycles per second; measured in hertz (Hz).

wavelength (λ)

Distance between successive crests (or troughs) of a wave.

speed of light (c)

c ≈ 3 × 10^8 m/s in vacuum.

photon

A quantum of light; a particle representing a quantum of energy E = h f.

Planck’s constant (h)

Constant linking energy and frequency: E = h f.

threshold frequency (f0)

Minimum frequency required to emit electrons in the photoelectric effect.

work function (W0)

Minimum energy required to emit a photoelectron from a surface.

photoelectric effect

Emission of electrons from a material (usually a metal) when illuminated by light above threshold frequency.

emission spectrum

Spectrum showing the specific wavelengths/lines emitted by an element.

absorption spectrum

Spectrum showing dark lines where light is absorbed by a substance.

continuous spectrum

Spectrum with light of all wavelengths within a range (e.g., sunlight).

line spectrum

Spectrum showing only specific discrete wavelengths emitted by an element.

electric charge

Property of matter that causes it to experience electrostatic forces; protons are positive, electrons are negative.

Coulomb’s Law

F ∝ k Q1 Q2 / r^2; electrostatic force between two charges.

electric field

Region around a charge where other charges experience a force; described by field lines.

electric field strength (E)

Force per unit charge: E = F/Q; also E = k Q / r^2.

Coulomb’s constant (k)

k ≈ 9 × 10^9 N m^2 C^−2.

potential difference (voltage, V)

Work done per unit charge to move a charge between points.

electromotive force (emf, ε)

Voltage provided by a source when no current flows; energy per unit charge.

internal resistance (r)

Resistance within a source (cell/battery) that causes energy loss.

Ohm’s Law

V = I R; current through a conductor is proportional to voltage at constant temperature.

series circuit

Circuit where components share the same current; voltages add; resistance adds.

parallel circuit

Circuit where components share the same voltage; currents split; total resistance decreases.

resistor

Component that resists the flow of current; described by its resistance.

transformer

Device that changes AC voltage and current levels via inductive coupling.

Faraday’s law

Induced emf is proportional to the rate of change of magnetic flux.

magnetic flux (Φ)

Product of magnetic field strength and area; unit Weber (Wb).

electromagnetic induction

Generation of current due to changing magnetic flux.

AC (alternating current)

Current that reverses direction periodically; sinusoidal in time.

DC (direct current)

Current that flows in one direction only.

right-hand rule (generator)

Rule to determine direction of induced current in generators.

Fleming’s left-hand rule

Rule to determine force, current, and motion in motors.

Fleming’s right-hand rule

Rule to determine induced current direction in generators.

RMS (root mean square)

Effective DC-equivalent value of an AC quantity (voltage or current).

root mean square voltage (Vrms)

Equivalent DC voltage producing same heating effect as AC.

root mean square current (Irms)

Equivalent DC current producing same heating effect as AC.

emf vs pd

Emf is the source’s voltage with no current; pd is the voltage across a component.

spectroscope

Optical instrument used to disperse light into its spectrum.

diffraction

Spreading of waves as they pass through slits or obstacles, forming spectra.

diffraction grating

Device with many closely spaced lines to separate light into spectrum.

emission spectra (line spectra)

Series of lines corresponding to transitions in atoms; unique to elements.

absorption spectra (dark lines)

Spectra with dark lines where light is absorbed by atoms.

photon energy (E = h f)

Energy of a photon proportional to its frequency.

absorption spectrum vs emission spectrum

Absorption shows dark lines; emission shows bright lines; combined spectra identify elements.

spectral line

A single wavelength (or frequency) present in a spectrum.

diffraction grating

Optical element with many narrow slits that diffracts light to reveal spectra.

visible light spectrum

Portion of the electromagnetic spectrum detectable by the human eye (roughly 400–700 nm).

Planck’s constant (h)

Fundamental constant linking energy and frequency: E = h f.

atomic emission spectrum

Discrete lines emitted by atoms as electrons drop to lower energy levels.

threshold frequency (f0)

Minimum frequency required for photoemission to occur.

work function (W0)

Minimum energy needed to remove an electron from a surface.

photoelectron

Electron ejected from a material due to photoelectric effect.

photoelectric diode

Device that uses the photoelectric effect to convert light into electrical signals.

electric flux (Φ)

Flow of electric field through a given area; related to the magnetic flux in Faraday’s law.

electric field lines

Imaginary lines showing direction of the electric field; they start on positive charges and end on negative charges.

gauge for units (SI)

Standard units used in physics (m, kg, s, A, K, mol, cd).