CAPE Physics Unit 1 key terms

The straight-line distance and direction of a point from its starting position, treated as a vector quantity. It differs from distance travelled, which is a scalar and ignores direction.

The rate of change of displacement with respect to time, a vector quantity with both magnitude and direction. Average velocity divides total displacement by total time taken.

The rate at which velocity changes with time, including changes in speed, direction, or both. It is measured in metres per second squared and is a vector.

The resultant force on a body equals the rate of change of its momentum; for constant mass this reduces to force equals mass times acceleration, measured in newtons.

The product of a body's mass and its velocity, a vector measured in kilogram metre per second. For a chosen system, total momentum is conserved when the net external impulse is zero; closure to matter alone does not establish isolation from force.

The time integral of resultant force, or average resultant force times duration, equal to the change in momentum of the chosen body or system. It is measured in newton seconds and explains why airbags reduce injury.

The inward radial component of the resultant force for circular motion; in nonuniform motion a tangential resultant component can also be present. It has magnitude mv squared divided by radius r.

The rate of change of angular displacement, measured in radians per second. It links linear speed to circular motion through the relation speed equals radius times angular velocity.

The turning effect of a force about a pivot, equal to the force multiplied by the perpendicular distance from the pivot to its line of action. Measured in newton metres.

For a body in rotational equilibrium, the sum of clockwise moments about any point equals the sum of anticlockwise moments about that same point.

The single point through which the entire weight of a body may be considered to act, whatever its orientation. Its position affects stability and toppling.

The ratio of the speed of light in a vacuum to the speed of light in a medium, For light incident from vacuum or approximately air, it also equals sin(incidence)/sin(refraction); for two general media that ratio is their relative refractive index.

The angle of incidence in the denser medium for which the angle of refraction in the less dense medium is exactly ninety degrees. Beyond it total internal reflection occurs.

The complete reflection of light back into a denser medium when it strikes the boundary at an angle of incidence greater than the critical angle. It is used in optical fibres.

The spreading of waves as they pass through an aperture or around an obstacle, becoming more pronounced when the wavelength is comparable to the gap or obstacle size.

The superposition of two or more waves to produce regions of reinforced and cancelled displacement. Constructive interference gives maxima; destructive interference gives minima.

Two wave sources that maintain a constant phase difference and have the same frequency, so that a stable interference pattern can be observed. Lasers provide a common example.

A wave pattern formed when two waves of equal frequency and amplitude travel in opposite directions, producing fixed nodes and antinodes. Energy is not transported along the medium.

The large-amplitude oscillation that occurs when a system is driven at a frequency matching one of its natural frequencies. It is used in tuning circuits and musical instruments.

The energy required to raise the temperature of one kilogram of a substance by one kelvin, measured in joules per kilogram per kelvin. It depends on the material.

The energy absorbed or released when a substance changes state at constant temperature, without change in temperature. Specific latent heat is quoted per kilogram of substance.

The total kinetic and potential energy of the particles within a system, arising from their random motion and intermolecular forces. It depends on temperature and state.

The lowest possible temperature, zero kelvin, at which particles have minimum kinetic energy. It cannot be reached exactly, though values very close have been achieved.

The relation that pressure times volume equals the number of moles times the universal gas constant times absolute temperature, valid for an ideal gas.

A consistent deviation of measurements from the true value in one direction, caused by faulty apparatus or flawed method. It affects accuracy but not necessarily precision.

Unpredictable variation in measurements about a mean value, caused by fluctuating conditions or limited resolution. It reduces precision and can be lessened by averaging repeated readings.

How close a measured value is to the accepted true value. It is affected mainly by systematic error, whereas precision concerns the spread of repeated readings.

The degree of agreement among repeated measurements of the same quantity, reflected in a small spread of values. It is affected by random error and instrument resolution.

A force directed toward equilibrium, often proportional to displacement over an explicitly specified linear range; its direction determines the sign in the oscillator equation.

The angular frequency of free oscillation in the chosen ideal model, measured in radians per second and related to period by omega = two pi divided by period.