Speed of Sound
The speed at which a pressure wave travels through an elastic medium.
Governing formula
v = √(K / ρ) (Fluids), v = √(γ R T / M) (Ideal Gas)
SI unit
m/s
In depth
Speed of sound depends on medium stiffness (bulk modulus K) and density ρ. In dry air at 20°C, speed of sound is ~343 m/s; in water ~1480 m/s; in steel ~5100 m/s.
Examples in the real world
Timing lightning flash vs thunder clap: a 3-second delay between flash and thunder indicates lightning struck ~1 km away.