Mach (20°C, 1 atm) to Centimeter per Hour

Mach number is the ratio of an object's speed to the speed of sound in the surrounding medium. Mach 1 at 20°C, 1 atm equals approximately 343.6 m/s (1,235 km/h).

Mach = velocity ÷ speed_of_sound. At 20°C: Mach 1 = 343.6 m/s. Speed of sound = √(γRT/M) where γ = heat capacity ratio.

To m/s (at 20°C): × 343.6. To km/h (at 20°C): × 1,237. Note: changes with altitude and temperature.

Fighter jets (Mach 1.5–2.5), commercial aircraft (Mach 0.8–0.85), space shuttle reentry (Mach 25), and missile speeds.

Concorde: Mach 2.04. SR-71 Blackbird: Mach 3.3. X-15: Mach 6.7. Meteorites enter at Mach 50+. Subsonic <1, supersonic >1, hypersonic >5.

Thinking Mach is constant — it varies with temperature/altitude. At 30,000 ft, Mach 1 ≈ 295 m/s (colder air = slower sound).

Mach 1 = speed of sound. Below Mach 1 = subsonic. Mach 1–5 = supersonic. Above Mach 5 = hypersonic. It's a ratio, not a fixed speed.

Centimeter per hour measures very slow movements in centimeters over an hour. Used for extremely gradual processes.

1 cm/h = 0.01 m/h = 0.00001 km/h = 0.00000278 m/s. Extremely small speed unit.

To m/s: ÷ 360,000. To m/h: × 0.01. To mm/h: × 10.

Very slow geological processes, material expansion/contraction measurements, and some biological growth studies.

Human nail growth: ~0.01 cm/h. Stalagmite formation: ~0.001 cm/h. Some coral growth: 0.1 cm/h.

Using for anything except very slow processes. Confusing with cm/min or cm/s.

100 cm/h = 1 m/h. Primarily a scientific measurement unit. Not for everyday use.