Physics Intro & Atomic Structure - Vocabulary Flashcards

Vocabulary-style flashcards covering key concepts from Week 1 and Week 2 lecture notes, including matter, energy, units, atomic structure, and electrostatics.

Natural science

The study of matter and its motion through space, related to energy and force, to understand how the universe behaves.

Physical science

Non-living matter (e.g., physics).

Biological science

Living matter (e.g., anatomy and physiology).

Matter

Anything that occupies space; built from atoms and molecules.

Mass

The quantity of matter in an object.

Energy

The ability to do work; a scalar quantity.

SI unit

The standard system of units used in science (MKS in this context).

MKS units

Meters, Kilograms, Seconds—the base units used in the SI system.

Base quantities

Fundamental quantities with their own units (e.g., length, mass, time, electric current).

Derived quantities

Quantities formed from base quantities (e.g., area, density).

Special quantities (radiography)

Radiography-specific measurements (e.g., exposure, dose, dose equivalent, activity).

Length

Base quantity with unit meters (m).

Mass (base quantity)

Base quantity with unit kilograms (kg).

Time

Base quantity with unit seconds (s).

Electrical current

Base quantity with unit ampere (A).

Derived unit (example)

Units like square meters (m^2) for area or kilograms per cubic meter (kg/m^3) for density.

Area

Derived quantity calculated as length × width (m^2).

Density

Derived quantity defined as mass/volume (kg/m^3).

Exposure (special unit)

Ability of an x-ray source to ionize air; units: C/kg or Roentgen.

Dose

Absorbed energy per unit mass; units: Gray (Gy) or rad.

Dose equivalent

Product of absorbed dose and radiation quality factor; units: sievert (Sv) or rem.

Activity

Number of nuclear transformations per unit time; units: Becquerels (Bq) or Curies (Ci).

Mechanics

Study of motion of objects; includes mass, inertia, and forces.

Inertia

Resistance to change in motion; follows Newton’s First Law.

Friction

Force that opposes motion between surfaces in contact.

Newton’s First Law

An object at rest stays at rest and an object in motion stays in motion unless acted on by a net external force (inertia).

Scalar quantity

A physical quantity described by magnitude only (e.g., speed, energy).

Vector quantity

A physical quantity described by magnitude, direction, and often sense (e.g., velocity).

Velocity

Rate of change of position with time; a vector quantity with direction; SI unit m/s.

Acceleration

Rate of change of velocity with time; SI unit m/s^2.

V = d/t

Formula for velocity: velocity equals distance divided by time.

Force

Push or pull on an object; SI unit newton (N); F = ma.

Mass vs. Force

Mass is the amount of matter; force is the interaction that causes acceleration (F = ma).

Weight

Force of gravity acting on mass; W = mg.

Momentum

Mass × velocity; SI unit kg·m/s; p = mv.

Work

Force applied over a distance; SI unit joule (J); W = Fd.

Power

Rate of doing work; SI unit watt (W); P = work/t or P = Fd/t; 1 W = 1 J/s.

Energy

Ability to do work; SI unit joule (J).

Potential energy

Energy stored due to position; PE = mgh.

Kinetic energy

Energy of motion; KE = 1/2 mv^2.

Law of Conservation of Energy

Energy cannot be created or destroyed; it can be transformed; total energy is conserved.

Electrical energy

Energy due to charge movement across a potential difference (voltage).

Chemical energy

Energy stored in chemical bonds; released in chemical reactions.

Thermal/Heat energy

Kinetic energy of molecules; related to temperature.

Nuclear energy

Energy in the nucleus of an atom; released in nuclear processes.

Electromagnetic energy

Energy carried by electromagnetic radiation (radio, light, x-rays, etc.).

EM radiation

Combination of electric and magnetic fields that travels through space; exhibits wave-particle duality.

Wavelength

Distance between successive crests of a wave; unit often angstroms for EM radiation.

Frequency

Number of cycles per second; unit hertz (Hz).

Velocity–frequency–wavelength relation

Velocity = frequency × wavelength (c = fλ); for EM, c ≈ 3×10^8 m/s.

Planck’s constant

Proportionality constant h linking energy and frequency: E = hν.

E = hν

Photon energy equals Planck’s constant times frequency.

Photon

Quantum of EM radiation; particle-like description of light.

Ionization

Removal of an electron from an atom; creates an ion pair.

Atomic number (Z)

Number of protons in the nucleus; identifies the element.

Atomic mass number (A)

Total number of protons and neutrons in the nucleus.

Isotopes

Same Z, different A (different number of neutrons).

Isobars

Different Z and different elements with the same A.

Isotones

Different Z and A but same number of neutrons.

Isomers

Same Z and A but different energy states (metastable states possible).

Orbital electrons

Electrons occupy orbitals around the nucleus; arranged in shells (K, L, M, N, O, P, Q).

Electron capacity (2n^2)

Maximum number of electrons in a given shell; example: O shell holds 50 electrons (2×5^2).

Binding energy

Energy required to eject an electron; greater for electrons closer to the nucleus.

Electron binding energy unit

Energy unit for binding energy, eV (electron volts).

Valence

Chemical bonding character of an atom; related to outer-shell electrons.

Octet rule

Atoms tend to have eight electrons in their outer shell for stability.

Atomic nomenclature – Z and A

Z = number of protons; A = protons + neutrons; indicates isotope identity.

Molecule

Two or more atoms bonded together; smallest unit of a compound.

Compound

Substance consisting of two or more elements in fixed ratio.

Electrostatics

Study of stationary electrical charges.

Charge

Property of matter; exists as positive or negative; movement of electrons transfers charge.

Electrification by contact

Charge transfer when two neutral objects touch and electrons redistribute.

Electrification by friction

Charge transfer through rubbing (triboelectric effect).

Electrification by induction

Charge separation caused by a nearby charged object; grounding neutralizes excess charge.

Ground (earthing)

Connecting to Earth to neutralize charge.

Lightning

Discharge of electricity between clouds or between cloud and Earth.

Coulomb’s Law

Electrostatic force ∝ product of charges and inversely ∝ square of distance; F ∝ Q1Q2/r^2.

Inverse Square Law

Force strength decreases with the square of the distance between charges.

First Law of Electrostatics (Repulsion–Attraction)

Like charges repel; opposite charges attract.

Second Law of Electrostatics (Inverse Square)

Coulomb’s law describing how force scales with distance.

Charge distribution on conductors

Charge tends to distribute uniformly on the surface of conductors.

Charge concentration at curvature

Charge concentrates more at areas with greater curvature.

Movement of charges on conductors

Negative charges tend to move along solid conductors.