ORELA Physics (NT308) key terms

A testable, falsifiable statement that predicts the outcome of an experiment under specified conditions; it must be phrased so that evidence could show it to be wrong.

A quantity that a researcher deliberately holds constant across all trials so that it cannot influence the measured result, allowing a fair comparison between experimental groups.

The digits in a measurement that carry meaningful information about its precision, including all certain digits plus one estimated digit at the end.

A method of checking or deriving equations by comparing the base units of each quantity, since both sides of a valid physical equation must have identical dimensions.

A repeatable inaccuracy that shifts measurements in the same direction, caused by faulty calibration or flawed procedure; averaging many trials does not reduce it.

A well-tested explanatory framework that accounts for a broad body of evidence and generates new predictions; unlike everyday usage, it does not mean a guess.

A viewpoint that is not accelerating, in which an object with no net force moves at constant velocity; Newton's laws hold in such frames without adding fictitious forces.

The net force on an object equals its mass times its acceleration; equivalently, force equals the rate of change of momentum.

The product of a force and the time interval over which it acts, equal to the change in an object's momentum; extending collision time reduces peak force.

In a system with no net external force, the total momentum of all interacting objects stays constant, which lets you analyze collisions and explosions without knowing the forces involved.

The acceleration of an object moving on a circular path, directed toward the center, with magnitude equal to the square of the speed divided by the radius.

A measure of how strongly an object resists angular acceleration, depending on its mass and on how that mass is distributed about the rotation axis.

The net work done on an object equals the change in its kinetic energy, linking force and displacement to changes in speed.

The state in which two objects in contact exchange heat at equal rates, so their temperatures stop changing; temperature determines the direction of heat flow.

The change in internal energy of a system equals the heat added to it minus the work it does, expressing conservation of energy for thermal processes.

A measure of how spread out energy is among the microscopic states of a system; it increases for any spontaneous process in an isolated system.

The energy needed to raise the temperature of one kilogram of a substance by one kelvin, reflecting how much thermal energy the material can store per degree.

The energy absorbed or released when a substance changes phase at constant temperature, such as melting or boiling, without changing its temperature.

An equation relating pressure, volume, amount in moles, and absolute temperature of a dilute gas: pressure times volume equals moles times the gas constant times temperature.

When two or more waves meet at a point, the resulting displacement is the sum of the individual displacements; this explains both constructive and destructive interference.

The change in observed frequency of a wave when the source, the observer, or both move relative to the medium, perceived as a higher or lower pitch.

The bending of a wave as it passes from one medium into another where its speed differs, described by Snell's law relating the angles and refractive indices.

The complete reflection of light back into a denser medium when it strikes a boundary at an angle greater than the critical angle.

The spreading of waves around obstacles and through openings, becoming pronounced when the opening is comparable in size to the wavelength.

The alignment of the oscillations of a transverse wave in one direction, used to filter light and to distinguish transverse from longitudinal waves.

The force per unit positive charge at a point in space, a vector quantity pointing away from positive charges and toward negative charges.

The work per unit charge needed to move a charge between two points in a circuit or field, commonly called voltage and measured in volts.

The ratio of charge stored on a conductor to the potential difference across it, determined by the geometry of the plates and the material between them.

The sum of currents entering a junction equals the sum leaving it, a statement of charge conservation applied to circuit nodes.

The amount of magnetic field passing through a given surface, equal to field strength times area times the cosine of the angle between them.

A changing magnetic flux through a loop induces an electromotive force in it, proportional to the rate of change of that flux.

An induced current flows in the direction whose own magnetic field opposes the change in flux that produced it, a consequence of energy conservation.

The emission of electrons from a metal surface when light of sufficiently high frequency strikes it, showing that light delivers energy in discrete packets.

A quantum of electromagnetic energy whose energy equals Planck's constant times the wave's frequency; the particle-like unit of light.

The wavelength associated with a moving particle, equal to Planck's constant divided by the particle's momentum, showing that matter has wave properties.

The principle that certain paired quantities, such as position and momentum, cannot both be known with unlimited precision at the same time.

The time required for half of the radioactive nuclei in a sample to decay, a constant characteristic of each isotope.

The slowing of a clock as measured in a frame moving relative to it, predicted by special relativity and significant only near light speed.