Basically the notes are about waves and the speed of sound.
- A vibrating source moves with simple oscillating motion
- A transverse wave is when the direction of wave travel is perpendicular to the motion of the source (for example, light)
- A longitudinal wave is when the direction of wave travel is parallel to the motion of the source (for example, sound)
- A cycle is a complete sequence of motion
- Wavelength, represented by l, is the length in metres of one cycle
- Period, represented by T, is the time it takes to complete one cycle in seconds
- Frequency (f): the number of cycles / time, measured in Hertz (Hz)
- Amplitude: the maximum displacement (height) of the wave from 0
- The wave equation is v = lf, which is derived from the kinematics formula v =Dd /Dt
- Dense areas of sound waves are compressions
- Less dense areas of sound waves are rarefactions
- Factors that affect the speed of sound: the producer, the temperature and density of its medium
- Stiffer materials result in a faster speed of sound
- vs = 332 m/s + (0.6 m/s ÷°C) (T °C)
- Speeds close to the speed of sounds are measured in Mach numbers
- < Mach 1 is subsonic
- > Mach 1 is supersonic
- Examples of planes/aircraft that have approached and surpassed the speed of sound include Concorde, while Boeing, although fast, is still subsonic
- The sound barrier is when pressure is built up when something approaches the speed of sound and catches up to its own sound waves, creating a "wall"
- A plane breaking the sound barrier creates cone-shaped shock waves that hit the Earth's surface, where the sound is heard as a "boom". This is a sonic boom.
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