Physics and Chemistry Definitions, Laws, and Principles

Vector

A physical quantity with magnitude and direction.

Scalar

A physical quantity with magnitude only.

Resultant vector

The single vector having the same effect as two or more vectors together.

Frame of reference

A coordinate system used to represent and measure properties of objects, such as position.

One dimensional motion

Motion along a straight line.

Distance

The total path length travelled.

Displacement

The difference in position in space.

Average speed

The total distance travelled per total time.

Average velocity

The rate of change of position.

Acceleration

The rate of change of velocity.

Instantaneous velocity

The rate of change in position, i.e. the displacement divided by a very small time interval or the velocity at a particular time.

Instantaneous speed

The magnitude of the instantaneous velocity.

Uniform/constant velocity

Motion at constant velocity, i.e. no acceleration.

Uniform accelerated motion

The velocity of an object changes with the same amount during each time interval.

Gravitational potential energy

The energy an object has because of its position in the gravitational field relative to some reference point.

Kinetic energy

The energy an object possesses as a result of its motion.

Mechanical energy

The sum of the gravitational potential energy and kinetic energy.

The law of the conservation of energy

The total energy of an isolated system remains constant.

Isolated system

A system that does not interact with its surroundings.

The principle of conservation of mechanical energy

The total mechanical energy in an isolated system/in the absence of dissipative forces remains constant.

Pulse

A single disturbance in a medium.

Transverse pulse

A pulse in which the particles of the medium move at right angles to the direction of motion of the pulse.

Amplitude

The maximum disturbance of a particle from its rest (equilibrium) position.

The principle of superposition

The algebraic sum of the amplitudes of two pulses that occupy the same space at the same time.

Constructive interference

The phenomenon where the crest of one pulse overlaps with the crest of another to produce a pulse of increased amplitude.

Destructive interference

The phenomenon where the crest of one pulse overlaps with the trough of another, resulting in a pulse of reduced amplitude.

Transverse wave

A wave in which the particles of the medium vibrate at right angles to the direction of motion of the wave.

Wavelength

The distance between two successive points in phase.

Frequency

The number of wave pulses per second.

Period

The time taken for one complete wave pulse.

Crest

Highest point (peak) on a wave.

Trough

Lowest point on a wave.

Wave speed

The distance travelled by a point on a wave per unit time.

Longitudinal wave

A wave in which the particles of the medium vibrate parallel to the direction of motion of the wave.

Compression

A region of high pressure in a longitudinal wave.

Rarefaction

A region of low pressure in a longitudinal wave.

Pitch

The effect produced in the ear due to the sound of a particular frequency. Pitch is directly proportional to frequency.

Loudness

A subjective term describing the strength of the ear's perception of a sound. Loudness is directly proportional to amplitude.

Photon

A packet of energy found in light.

Magnetic field

A region in space where a magnet or ferromagnetic material will experience a force (non-contact).

Ferromagnetic materials

Materials that are strongly attracted by magnets and are easily magnetised. Examples are iron, cobalt, nickel and their alloys.

Non-contact force

A force exerted on an object without touching the object.