Velocity of Sound in Sea Water (20°C, 10m depth) to Cosmic Velocity - First

The speed of sound in seawater at 20°C and 10 meters depth is approximately 1,522 m/s, varying with temperature, salinity, and pressure.

Complex function of T, S, P. Mackenzie equation: c ≈ 1,449 + 4.6T - 0.055T² + 0.00029T³ + (1.34-0.01T)(S-35) + 0.016z. Typical: ~1,500 m/s.

To km/h: × 3.6. To ft/s: × 3.281. 1,522 m/s = 5,479 km/h = 3,404 mph.

Naval sonar, commercial ship echo sounders, underwater positioning systems, and marine seismic surveys.

Sound speed increases ~1.3 m/s per °C, ~1.3 m/s per PSU salinity, and ~1.7 m/s per 100m depth. SOFAR channel at ~1000m depth traps sound for thousands of km.

Using a single constant — sound speed in the ocean varies significantly with depth and location. Always measure or calculate for local conditions.

~1,500 m/s is a good approximation. Remember: warmer, saltier, deeper = faster sound. Critical for accurate sonar ranging.

The first cosmic velocity (escape velocity from Earth's surface to orbit) is approximately 7,900 m/s (7.9 km/s), the minimum speed needed to achieve Earth orbit.

v₁ = √(GM/r) where G is gravitational constant, M is Earth's mass, r is Earth's radius. Approximately 7.9 km/s.

To km/h: × 3,600. To mph: × 17,672. 7.9 km/s = 28,440 km/h = 17,672 mph.

Minimum speed for satellites, space station orbit, and low Earth orbit (LEO) calculations.

ISS orbits at ~7.66 km/s. Below this speed, you fall back to Earth. Above it, you stay in orbit (if horizontal).

Confusing with escape velocity (second cosmic velocity, 11.2 km/s) — orbital velocity is lower.

Remember: ~8 km/s for orbit, ~11 km/s to escape. v₁ is minimum for orbit, not escape.