In a compressible sound transmission medium - mainly air - air particles get an accelerated motion: the
particle acceleration or sound acceleration with the symbol a in
metre/second². In
acoustics or
physics,
acceleration (symbol:
a) is defined as the rate of change (or time
derivative) of
velocity. It is thus a
vector quantity with dimension
length/
time². In
SI units, this is m/s².
To accelerate an object (air particle) is to change its velocity over a period of time. Acceleration is defined technically as "the rate of change of velocity of an object with respect to time" and is given by the equation
- <math>
mathbf = </math>
where
- a is the acceleration vector
- v is the velocity vector expressed in m/s
- t is time expressed in seconds.
This equation gives
a the units of m/(s·s), or m/s² (read as "metres per second per second", or "metres per second squared").
An alternative equation is:
- <math>
mathbf = </math>
where
- <math>mathbf</math> is the average acceleration (m/s²)
<math>mathbf</math> is the initial velocity (m/s)
<math>mathbf</math> is the final velocity (m/s)
<math>t</math> is the time interval (s)
Transverse acceleration (perpendicular to velocity) causes change in direction. If it is constant in magnitude and changing in direction with the velocity, we get a
circular motion. For this
centripetal acceleration we have
- <math> mathbf = -......
...
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