ORT Physics flashcards

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

Newton's second law

The resultant force on a body equals the rate of change of its momentum; for constant mass this reduces to F = ma, with force in newtons.

Conservation of momentum

In any collision or interaction with no external resultant force, the total momentum before equals the total momentum after, treated as a vector quantity.

Centripetal acceleration

For an object moving in a circle of radius r at speed v, the acceleration is v squared divided by r, directed toward the centre of the circle.

Work-energy theorem

The net work done on an object by all forces equals its change in kinetic energy, allowing problems to be solved without resolving forces over time.

Elastic potential energy

Energy stored in a stretched or compressed spring obeying Hooke's law, given by one half times the spring constant times the extension squared.

Projectile motion

Motion under gravity alone with constant horizontal velocity; the vertical component accelerates at g, and time of flight depends only on the vertical component.

Ideal gas law

pV = nRT relates pressure, volume, amount in moles and absolute temperature; R is 8.31 joules per mole per kelvin, and T must be in kelvin.

First law of thermodynamics

The change in internal energy of a system equals heat supplied to it minus work done by it, a statement of energy conservation for thermal processes.

Mean molecular kinetic energy

For a gas at thermodynamic temperature T, the average translational kinetic energy per molecule is three halves times k times T, independent of gas identity.

Root-mean-square speed

A representative molecular speed equal to the square root of the mean of the squared speeds; it rises with temperature and falls with greater molecular mass.

Adiabatic process

A change with no heat exchange with the surroundings, so Q equals zero and internal energy change equals minus the work done by the gas.

Specific latent heat

The energy needed to change the phase of one kilogram of a substance at constant temperature, without any change in its temperature.

Carnot efficiency

The maximum possible efficiency of a heat engine operating between hot and cold reservoirs, equal to one minus the ratio of their absolute temperatures.

Coulomb's law

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

Resistors in parallel

The reciprocal of the total resistance equals the sum of the reciprocals of the individual resistances; the voltage across each branch is the same.

Electrical power

The rate at which electrical energy is transferred, given by P = VI, and equivalently by I squared R or V squared divided by R for a resistor.

Magnetic force on a charge

A charge q moving at speed v in a field B experiences force qvB sin theta, directed perpendicular to both the velocity and the magnetic field.

Faraday's law of induction

The induced emf in a coil equals the negative rate of change of magnetic flux linkage, with the negative sign reflecting Lenz's law opposition.

Capacitor energy storage

The energy stored in a charged capacitor is one half times capacitance times voltage squared, or equivalently one half times charge times voltage.

Uniform field between plates

Two parallel conducting plates at potential difference V separated by distance d produce a uniform field of magnitude V/d between them.

Snell's law

When light crosses a boundary between media, the product of refractive index and sine of the angle to the normal is constant on both sides.

Critical angle

The angle of incidence in the denser medium for which the refracted ray grazes the boundary; beyond it, total internal reflection occurs.

Thin lens equation

One over focal length equals one over object distance plus one over image distance; magnification is image distance divided by object distance.

Young's double slit

Two coherent sources produce interference; bright fringes occur where path difference is a whole number of wavelengths, with spacing proportional to wavelength.

Diffraction grating equation

Maxima occur where d sin theta equals n times the wavelength, giving much sharper and more widely separated maxima than a two-slit arrangement.

Photoelectric equation

The maximum kinetic energy of emitted photoelectrons equals photon energy minus the work function; no emission occurs below the threshold frequency.

Photon energy

The energy carried by a single photon equals Planck's constant times frequency, or Planck's constant times the speed of light divided by wavelength.

Half-life

The time for half the nuclei in a radioactive sample to decay; it is constant for a given isotope and equals the natural logarithm of two divided by the decay constant.

de Broglie wavelength

The wavelength associated with a moving particle equals Planck's constant divided by its momentum, becoming significant only for very small masses.

Binding energy per nucleon

The energy released when nucleons bind, divided by nucleon number; it peaks near iron-56, so fusion releases energy for lighter nuclei and fission for heavier ones.

Combining uncertainties

For sums and differences, absolute uncertainties add; for products and quotients, percentage uncertainties add; for a power, multiply by the exponent.

Systematic versus random error

A systematic error shifts all readings consistently, often from faulty calibration; a random error scatters readings about a mean and is reduced by averaging repeats.