Armenia Physics Unified Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Kinematic equation for velocity

For constant acceleration, the velocity at time t is v = v0 + at, where v0 is the initial velocity and a is the constant acceleration.

Newton's second law

The net force on an object equals its mass times its acceleration, ΣF = ma; acceleration points in the direction of the net force.

Conservation of momentum

In an isolated system with no external net force, the total momentum Σmv stays constant through collisions and explosions, regardless of whether kinetic energy is conserved.

Static equilibrium conditions

A rigid body stays at rest only when the net force is zero and the net torque about any axis is also zero.

Centripetal acceleration

An object moving in a circle of radius r at speed v has acceleration v²/r directed toward the center; this is produced by a net inward force.

Work–energy theorem

The net work done on an object equals the change in its kinetic energy, W_net = mv²/2 − mv0²/2.

Ideal gas law

For an ideal gas, pressure times volume equals the number of moles times R times absolute temperature, pV = nRT.

First law of thermodynamics

The change in internal energy equals heat added to the system minus work done by the system, ΔU = Q − W.

Absolute temperature and molecular energy

The average translational kinetic energy of a gas molecule is (3/2)kT, depending only on absolute temperature, not on the gas species.

Heat engine efficiency

Efficiency equals useful work divided by heat absorbed from the hot reservoir, η = W/Q_hot = 1 − Q_cold/Q_hot.

Relative humidity

The ratio of the actual water-vapor pressure in air to the saturation vapor pressure at the same temperature, usually expressed as a percentage.

Coulomb's law

The electric force between two point charges is k·q1·q2/r², attractive for opposite signs and repulsive for like signs.

Ohm's law

For a conductor at constant temperature, current equals voltage divided by resistance, I = U/R.

Faraday's law of induction

The induced emf in a loop equals the negative rate of change of magnetic flux through it, ε = −N·ΔΦ/Δt.

Lenz's law

The direction of an induced current is such that its magnetic field opposes the change in flux that produced it.

Resistors in parallel

For parallel resistors the reciprocal of total resistance equals the sum of reciprocals, and the voltage across each branch is the same.

Magnetic force on moving charge

A charge q moving at speed v in field B experiences force qvB·sinθ, perpendicular to both velocity and field; a charge at rest feels none.

Period of a spring oscillator

A mass m on a spring of stiffness k oscillates with period T = 2π√(m/k), independent of amplitude for small oscillations.

Wave speed relation

Wave speed equals wavelength times frequency, v = λf; frequency is set by the source and stays constant across media.

Resonance condition

Resonance occurs when the driving frequency matches a system's natural frequency, producing maximum amplitude and efficient energy transfer.

Snell's law

At a boundary between media, n1·sinθ1 = n2·sinθ2, relating refractive indices to the angles of incidence and refraction.

Total internal reflection

Light traveling from a denser to a less dense medium is completely reflected when the incidence angle exceeds the critical angle.

Thin lens equation

The focal length, object distance, and image distance satisfy 1/f = 1/d_o + 1/d_i; virtual images correspond to negative image distance.

Photoelectric equation

The maximum kinetic energy of emitted electrons is Ek_max = hf − A, where A is the work function of the metal.

Photon energy

A photon carries energy E = hf = hc/λ, so shorter wavelength means higher energy per photon.

Bohr hydrogen energy levels

Hydrogen levels are E_n = −13.6 eV/n²; a photon of energy hf = E_high − E_low is emitted in a downward transition.

de Broglie wavelength

A particle with momentum p has an associated wavelength λ = h/p, which explains wave behavior such as electron diffraction.

Half-life

The time in which half the radioactive nuclei in a sample decay; activity falls by half each half-life and N = N0·e^(−λt).

Beta-minus decay

A neutron converts to a proton, emitting an electron and antineutrino; the mass number A stays the same while Z increases by one.

Measurement uncertainty

A measured value is reported as mean ± absolute uncertainty, often taken as half the smallest instrument division for a single reading.

Linear graph slope

For a straight-line graph, the slope equals the change in the vertical quantity divided by the change in the horizontal quantity, with units of their ratio.

Significant figures rule

A calculated result should carry no more significant figures than the least precise input value used in the computation.