Kilometer per Second to Foot per Second

Earth orbits the Sun at an average of about 29.8 km/s (107,000 km/h). This speed varies slightly because Earth's orbit is elliptical — it moves fastest in January (perihelion) at 30.3 km/s and slowest in July (aphelion) at 29.3 km/s. You're traveling at this speed right now relative to the Sun.

Escape velocity is the minimum speed needed to leave a body's gravitational influence without further propulsion. From Earth's surface it's 11.2 km/s. From the Moon it's 2.4 km/s. From the Sun's surface it's 617.5 km/s. The Voyager 1 spacecraft left Earth's sphere of influence at about 16.6 km/s.

Primary (P) waves travel at 5–8 km/s through Earth's crust, reaching 13 km/s in the mantle and core. Secondary (S) waves travel at roughly 60% of P-wave speed. This speed difference is why seismologists can calculate earthquake distance — the gap between the P and S wave arrival times reveals how far the sensor is from the epicenter.

Meteoroids enter Earth's atmosphere at 11–72 km/s, depending on whether they're moving with or against Earth's orbital direction. The friction at these speeds heats them to incandescence — the streak of light visible as a 'shooting star'. Most disintegrate completely above 80 km altitude. The upper bound of 72 km/s is the sum of Earth's orbital speed plus the body's own velocity.

A typical high-powered rifle round (e.g. 7.62×51mm NATO) travels at about 0.85 km/s (850 m/s or 3,060 km/h). Purpose-built anti-materiel rifles reach ~1.0 km/s. Railgun projectiles in military experiments have exceeded 3 km/s. All of these are far below orbital speed — getting to orbit requires speed, not just height.

A professional golfer's driver launches the ball at roughly 250 ft/s (170 mph). An amateur averages about 190–220 ft/s. The PGA Tour record ball speed is around 330 ft/s (225 mph), set by long-drive competitors using specialised equipment. For comparison, a tennis serve reaches about 180 ft/s and a baseball pitch about 150 ft/s — making a driven golf ball one of the fastest objects in non-motorised sport.

A skydiver in a stable spread-eagle position reaches terminal velocity at approximately 120 mph (176 ft/s) after about 10 seconds of freefall. In a head-down dive position, terminal velocity can reach 200+ mph (293+ ft/s). With a deployed parachute, descent slows to about 10–17 ft/s (7–12 mph) for a safe landing.

Vertical speed indicators in aircraft (VSI) use feet per minute because typical climb and descent rates produce sensible numbers — a commercial aircraft climbs at 1,500–2,500 ft/min, and descends at 300–500 ft/min for approach. In ft/s these would be 25–42 and 5–8 respectively — workable, but ft/min produces rounder pilot-friendly numbers for the ranges encountered.

Foot per second squared (ft/s²) is the imperial unit of acceleration. Standard gravitational acceleration is 32.174 ft/s² — meaning a falling object gains 32 ft/s of speed every second. This is used in US aerospace and artillery calculations. Engineers must be careful not to confuse ft/s (speed) with ft/s² (acceleration), as the units look similar but represent entirely different physical quantities.

One knot is approximately 1.6878 ft/s (or 1 nautical mile per hour). This means 100 knots is about 169 ft/s. Aircraft airspeed is measured in knots by international convention, but US military aircraft radar tracks and some engineering documents also express speeds in ft/s for compatibility with imperial-unit weapon system specifications.