Mile per Second to Foot per Second

The speed of light in a vacuum is exactly 299,792,458 m/s, which converts to approximately 186,282.397 mi/s. Before the SI system was globalised, US and British scientific texts routinely used this figure. The value 186,000 mi/s appears as a rounded approximation in older textbooks. Today, physicists universally use c = 3 × 10⁸ m/s or the exact SI value.

The solar wind — a stream of charged particles ejected from the Sun's corona — travels at roughly 250–500 mi/s (400–800 km/s) depending on whether it is the slow or fast component. During coronal mass ejections, bursts can exceed 1,200 mi/s (2,000 km/s). At 500 mi/s the solar wind crosses the 93-million-mile Earth–Sun gap in about 2 days, which is why space weather forecasters can give roughly 48 hours' notice before a geomagnetic storm hits.

Yes — several. NASA's Parker Solar Probe reached about 430,000 mph (119 mi/s or 192 km/s) at perihelion, making it the fastest human-made object ever. High-powered railgun projectiles tested by the US Navy reached around 2.5 km/s (1.5 mi/s). Intercontinental ballistic missiles (ICBMs) reach approximately 4 mi/s during their boost phase.

Exactly one second — that's the definition. At 1 mi/s you would cross the Atlantic Ocean (about 3,400 miles) in under an hour, reach the Moon (238,855 miles) in about 2.8 days, and reach the Sun (93 million miles) in roughly 12 days. The speed is conceptually useful for calibrating astronomical distances in imperial terms.

Rarely. The main residual use is in some US military ballistics documents and historical astrophysics references. The International Astronomical Union and NASA primarily use km/s for planetary and solar system speeds, and AU/year or c (fraction of light speed) for interstellar scales. Mi/s survives mostly in popular science writing aimed at American audiences unfamiliar with metric.

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.