Cosmic Velocity - Second to Foot per Second

The second cosmic velocity (Earth's escape velocity) is approximately 11,200 m/s (11.2 km/s), the minimum speed to escape Earth's gravity completely.

v₂ = √(2GM/r) = √2 × v₁ ≈ 11.2 km/s. Exactly √2 times the first cosmic velocity.

To km/h: × 3,600. To mph: × 25,000. 11.2 km/s = 40,320 km/h = 25,053 mph.

Moon missions, Mars missions, deep space probes (Voyager, New Horizons), and any mission leaving Earth's gravity well.

Apollo missions: ~11.2 km/s. Voyager probes: exceeded v₂ to leave solar system. New Horizons: launched at record 16.26 km/s (fastest ever from Earth).

Thinking you need this speed everywhere — you only need it at launch. In space, much less Δv is needed.

~11 km/s to escape Earth. √2 × orbital velocity. Remember: orbit ≈ 8 km/s, escape ≈ 11 km/s.

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.