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| Thermal energy (heat) is the non-mechanical transfer of energy between a system and its surroundings. |
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| A measure of the average kinetic energy of the molecules in a substance. |
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| A measurement; one mole of any substance is equal to the amount of that substance that contains the same number of atoms as 0.012 kg of carbon-12 (12C). |
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| The internal energy of a substance is the total potential energy and random kinetic energy of the molecules of the substance. |
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| Thermal (Heat) capacity is the energy required to raise the temperature of a body by 1 K |
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| Specific heat capacity is the energy required to raise a unit mass of a substance by 1 K. |
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| Pressure is the force per unit normal area (i.e. the area at right angles to the force). |
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| This is the number of atoms in 0.012 kg of carbon-12 (12C), i.e. in one mol. It is 6.02 × 10–23. |
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| Process by which individual molecules (the faster-moving ones) leave the surface of a liquid and enter the gas phase. Only takes place at the surface of the liquid at temperatures below the liquid’s boiling point. |
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| Boiling is the process by which the molecules of a liquid spontaneous change from the liquid phase into the gas phase throughout the body of the liquid. |
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| Damping involves a force that is always in the opposite direction to the direction of motion of the oscillating particle and is a dissipative force (i.e. the oscillating particle loses energy). |
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| It is possible to force a system to oscillate at any frequency by subjecting it to a changing force at that frequency. Such oscillations are forced oscillations |
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| The frequency f is the number of completed oscillations in a given period of time, SI unit: Hz (number of oscillations per second). |
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Definition
| If a system is temporarily displaced from its equilibrium position, it will oscillate at its natural frequency of vibration. |
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Definition
| Resonance occurs when a system is subject to an oscillating force at exactly the same frequency as the natural frequency of oscillation of the system. |
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| Simple harmonic motion (SHM) |
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Definition
| Simple harmonic motion (SHM) is motion where the acceleration of an object is always directed towards a fixed point and is proportional to its displacement from that fixed point. |
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Definition
| The phase difference, φ , is a measure of how ‘in step’ different particles are. |
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Definition
| The period T is the time taken for one complete oscillation. In other words, it is the time taken for one complete wave to pass any given point. |
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Definition
| The amplitude in simple harmonic motion (SHM) is the maximum displacement from the mean position during one oscillation. |
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Definition
| The displacement of an object is the distance from the origin in a particular direction. |
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Definition
| Progressive (travelling) waves transfer energy. This transfer is achieved by oscillations of the medium through which the wave travels but there is no net motion of the medium. |
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Definition
| Compressions are the points on a longitudinal wave where all the particles are ‘bunched together’ (high pressure). |
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Definition
| Rarefactions are the points on a longitudinal wave where all the particles are ‘far apart’ (low pressure). |
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Definition
| The crest is the peak of a transverse wave (the point of maximum positive displacement). |
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| The trough is the lowest point of a transverse wave (the point of maximum negative displacement). |
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Definition
| Transverse waves involve oscillations that are perpendicular to the direction of energy transfer. Light waves (all EM waves) are transverse. |
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Definition
| Longitudinal waves involve oscillations that are in the same direction as the direction of energy transfer. Sound waves are longitudinal. |
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Definition
| All electromagnetic waves travel with the same speed in a vacuum (free space). Typical approximate wavelengths are: |
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Definition
| The wave speed (in m s–1) is the speed at which the wave pattern passes a stationary observer (i.e. the speed of energy transfer by the wave). V=λF |
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Definition
| The wavelength λ is the shortest distance (in m) between two points that are in phase with one another (for example, the distance between adjacent crests on a transverse wave or adjacent compressions on a longitudinal wave). |
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Definition
| A surface at right angles to the direction of energy transfer of the wave consisting of points in phase. |
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Definition
The intensity of a wave is the power per unit area that is received by the observer. It is related to the amplitude of the wave.
I = P/A |
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Definition
Change in velocity per unit time OR
Rate of change of velocity. |
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Definition
Change in momentum (Δp)
OR
Force x time during which the force is applied |
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Definition
The quantity of motion of a moving body, measured by:
mass x velocity |
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Definition
The rate of working,
Work/Time |
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| Specific latent heat of fusion |
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Definition
| The amount of (thermal) energy needed to convert a unit mass of a solid substance into a liquid at the melting temperature of the substance / at constant temperature. |
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| Specific Latent Heat of Vaporization |
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Definition
Quantity of thermal energy/heat required to convert unit mass / mass of 1 kg
of liquid to vapour/gas; With no change of temperature / at its boiling point. |
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Definition
| Average speed: is the distance traveled divided by the time taken. |
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Definition
| Rate of change of distance at a given instant (in time) |
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Definition
| Total displacement traveled divided by the time taken |
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Definition
| Every object continues in a state of rest or uniform motion in a straight line unless acted upon by an external force. |
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Definition
The rate of change of momentum of a body is proportional to the resultant force and occurs in the direction of the force.
OR
The acceleration of a body is proportional to the resultant force and occurs in the direction of the force. |
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Term
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Definition
| When two bodies A and B interact, the force that A exerts on B is equal and opposite to the force that B exerts on A. |
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Definition
| The mass of one mole of a substance. |
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Definition
| Amount of energy per unit mass absorbed or released during a change of phase. (Solid->Liquid = fusion) |
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| Kinetic Theory of Gases (Assumptions of Ideal Gases) |
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Definition
1) Newton's laws apply to molecular behavior.
2) No intermolecular forces (except in collisions).
3) The molecules are in random motion.
4) The collisions between the molecules are elastic.
5) No time spent on collisions in comparison to time spent between collisions.
6) Volume of individual gas molecules negligible when compared to volume of container. |
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Definition
| Measure of rate of motion denoted by ω. Important for SHM. |
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| The Principle of Superposition. |
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Definition
| When two waves of the same type meet, the resulting disturbance at any point and at any time where the waves meet is just the vector sum of the disturbances that would have been produced by each of the individual waves. |
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Term
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Definition
| When two identical waves meet at a point and the waves are exactly (180°) out of phase, the resulting wave has zero amplitude – the two waves cancel each other. |
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| Constructive Interference |
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Definition
| When two identical waves meet at a point and the waves are exactly in phase, the resulting wave has twice the amplitude of either of the original waves. |
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Term
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Definition
| A wave reflected at the boundary between two media stays in its original medium. Its direction of travel is such that the incident angle (the angle between the incident ray and the normal) and the reflected angle (the angle between the reflected ray and the normal) are equal. |
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Term
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Definition
| A wave transmitted across the boundary between two media moves from one medium into the other. Its direction of travel changes as a result of refraction as calculated by Snell’s law. |
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Term
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Definition
| Diffraction is the phenomenon of the spreading of a wave after an aperture or obstacle. It is the process by which wave energy is received in the geometric shadow region after an obstacle or gap. |
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Term
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Definition
When a wave is refracted between two media, the ratio of the angle of incidence to the angle of refraction is a fixed constant that depends on the speeds of wave in each media.
n1/n2 = sin(θ1) / sin (θ2) |
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Term
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Definition
The difference in the total lengths of the two routes from source to that point.
(Interference often takes place at a given point in space as a result of there being two different routes for the wave energy to travel from source to that point.) |
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