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Bolt covered 100 m in 9.58 s — 10.44 m/s, 37.6 km/h. A 4.5-second 0–100 launch is 0.63 g. Three seconds of free fall is 106 km/h.
The three motion questions of physics class — how fast (v = d/t), how quickly it speeds up (a = Δv/t), and what gravity does (v = 9.81t, d = 4.9t²) — answered with real-unit conversions so the m/s answer also arrives in km/h, mph, and g-force.
Bolt averaged 10.44 m/s over 9.58 s; a 4.5-second 0–100 launch is 0.63 g; 3 seconds of free fall is 105.9 km/h — v=d/t, a=Δv/t, and gravity.
Speed is how fast; velocity adds direction (60 km/h east); acceleration is how fast the velocity changes — including slowing down and turning. The units cascade: meters, meters-per-second, meters-per-second-per-second. The non-obvious part: acceleration includes direction change — a car circling a roundabout at constant 30 km/h is accelerating continuously (centripetal, toward the center), which is why your body feels pushed outward. And "deceleration" is just negative acceleration, same physics. Real-world feel: elevators accelerate at ~1 m/s² (0.1 g, that stomach lift), sports cars at 6–8 m/s², emergency braking at 8–10 m/s², and a sneeze launches droplets at up to 40 m/s — faster than Bolt by 4×.
In a vacuum, everything accelerates at 9.81 m/s² regardless of mass — the hammer-and-feather demo Apollo 15 ran on the Moon. After 1 second: 9.8 m/s; 3 seconds: 29.4 m/s (106 km/h) having fallen 44 m; 10 seconds: 98 m/s over 490 m. Air ruins the purity fast: drag scales with speed squared, so objects reach terminal velocity where drag balances weight — skydivers ~53 m/s (190 km/h) belly-down, ~90 m/s head-down, a raindrop ~9 m/s, a penny ~20 m/s (enough to sting, not to kill — the Empire State myth fails because the coin tumbles and drag-caps early). Cats famously survive high falls partly because their terminal velocity (~27 m/s) plus leg-spreading is survivable — physics with whiskers.
Sports: sprint coaches time 10 m splits because velocity = distance ÷ split — a 1.80 s flying 10 m is 5.56 m/s, and top-end speed separates positions (elite wide receivers hit 9–10 m/s). Ball exit velocity = distance math inverted: a 120 mph baseball exit is 53.6 m/s. Driving: the two-second rule is velocity applied — at 100 km/h you cover 56 m in 2 s, which is why following distance is measured in time, not car lengths. Reaction distance is v × reaction time: at 100 km/h with a 1.5 s reaction, you travel 42 m before the brake is even touched — more than a third of a football field, which is the entire argument against phone-glancing at speed. Convert any "how fast was that" into m/s with ÷3.6 from km/h or ÷2.237 from mph.