Cosmic Velocity - Second to Kilometer per Hour

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.

Kilometer per hour measures the number of kilometers traveled in one hour. It's the most common speed unit for vehicles and everyday speed references in metric countries.

1 km/h = 1/3.6 m/s = 0.2778 m/s. There are 3600 seconds in an hour and 1000 meters in a kilometer.

To m/s: ÷ 3.6. To mph: × 0.621. To ft/s: × 0.911. To knots: × 0.540.

Speed limits (50 km/h urban, 100–130 km/h highway), vehicle speedometers, cycling speeds, marathon pace, and wind speed forecasts.

World's fastest train: 603 km/h (maglev). Commercial aircraft cruise: 850–950 km/h. Formula 1 top speed: 372 km/h. Hurricane winds: 119+ km/h.

Directly converting km to km/h without accounting for time. Also, confusing km/h with m/s in physics problems (always convert to SI).

Divide by 3.6 to convert to m/s. Quick approximation: 60 km/h ≈ 17 m/s. Remember: km/h ÷ 3.6 = m/s.