Cosmic Velocity - First to Foot per Second

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.

Foot per second measures the number of feet traveled in one second. Commonly used in engineering, ballistics, and some sports in the United States.

1 ft/s = 0.3048 m/s exactly (by definition of the international foot). 1 ft/s = 0.6818 mph.

To m/s: × 0.3048. To km/h: × 1.097. To mph: × 0.682. To knots: × 0.592.

Bullet velocities (handgun: 800–1,200 ft/s; rifle: 2,500–4,000 ft/s), waterfall flow rates, industrial conveyor speeds, and skydiving terminal velocity (120 ft/s).

Speed of sound: 1,125 ft/s at sea level. Free fall: 32 ft/s² acceleration. Skydiver terminal velocity: 120 ft/s. Baseball pitch: 132 ft/s (90 mph).

Confusing ft/s with mph — 1 ft/s is only 0.68 mph, not 1 mph. Also, mixing up ft/s and ft/min in HVAC calculations.

1 ft/s ≈ 0.3 m/s or ≈ 1.1 km/h. Quick check: 100 ft/s ≈ 70 mph. Multiply ft/s by 0.68 for approximate mph.