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To convert m/s to km/h, multiply by 3.6. So 10 m/s = 36 km/h, 30 m/s = 108 km/h, and 100 m/s = 360 km/h. The factor 3.6 comes from: 1 m/s = 1 m/s × (3,600 s/hr) ÷ (1,000 m/km) = 3.6 km/h. Simple and exact.
The 100 m sprint world record by Usain Bolt (9.58 seconds) translates to an average speed of 10.44 m/s = 37.58 km/h. His peak speed was about 12.4 m/s = 44.6 km/h. Physics and athletics track world records in m/s; road contexts use km/h — converting between them reveals whether a physical speed is fast in everyday terms.
Did you know? The speed of sound in dry air at 20°C is approximately 343 m/s = 1,234.8 km/h = 767 mph. Aircraft breaking the sound barrier must exceed Mach 1 — meaningful in m/s for aerodynamics equations but quoted in km/h for public news.
Weather stations and anemometers report wind speed in m/s for technical purposes, but forecasts quote km/h. Physics homework and engineering calculations use m/s; real-world comparisons (is this wind safe to drive in?) use km/h. Athletics biomechanics analyze sprint speeds in m/s while broadcasters describe them in km/h for audiences.