Abitur Physics flashcards

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

Displacement

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.

Velocity

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.

Acceleration

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.

Newton's second law

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.

Momentum

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.

Impulse

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.

Centripetal force

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.

Angular velocity

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.

Moment of a force

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.

Principle of moments

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

Centre of gravity

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.

Refractive index

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.

Critical angle

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.

Total internal reflection

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.

Diffraction

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.

Interference

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

Coherent sources

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.

Standing wave

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.

Resonance

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.

Capacitance

The charge stored per unit potential difference across a capacitor, measured in farads. For a parallel-plate capacitor it equals permittivity times area divided by plate separation.

Time constant

For a capacitor-resistor circuit, the product of resistance and capacitance; it is the time for the charge to fall to about thirty-seven per cent of its initial value during discharge.

Electric field strength

The force per unit positive charge experienced at a point in an electric field, measured in newtons per coulomb. It is a vector quantity with direction along the field line.

Potential difference

The energy transferred per unit charge when charge moves between two points in a circuit, measured in volts. It is the work done per coulomb.

Electromotive force

The energy supplied by a source per unit charge driven around a complete circuit, measured in volts. It differs from terminal potential difference when internal resistance is present.

Internal resistance

The resistance within a source of electromotive force that causes the terminal potential difference to fall as the current drawn increases. It dissipates energy as heat inside the source.

Electromagnetic induction

The generation of an electromotive force in a conductor when the magnetic flux linking it changes. The induced emf is proportional to the rate of change of flux linkage.

Magnetic flux

The product of the magnetic flux density and the area perpendicular to it, measured in webers. Flux linkage multiplies this by the number of turns in a coil.

Lenz's law

The direction of an induced current is such that it opposes the change producing it. This is a consequence of conservation of energy and gives the negative sign in Faraday's law.

Specific heat capacity

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.

Latent heat

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.