The speed of an object is the magnitude of its velocity. Sometimes people confuse speed with velocity but they’re actually not the same thing. Velocity is a vector quantity, so it has a directional component. Speed is a scalar quantity and does not take direction into account.

The SI unit of speed is the metre per second but its most common unit is the kilometre per hour.

Units of speed

• metre per second (m/s)
• kilometre per hour (km/h)
• mile per hour (m/h)
• knot (knot)
• foot per second (ft/s)

Interesting facts about speed

• Galileo was the first scientist to measure speed as distance over time (v = d / t).
• The speed of light is equivalent to 186,282 miles per second.
• Your tongue is the fastest healing part of your body
• A dolphin’s top speed is 37mph.
• An elephant can run up to 40 km/h.
• The fastest dog breed is the Greyhound and it can reach a speed of up to 45 mph.

Fastest Man on Earth and his average speed

Usain Bolt is the fastest man in the world and the record holder in the 100 and 200 metre sprints. Because we know how long it took Usain to run 100 and 200 metres, we can find out his average speed.

It took him 9.58 seconds to run 100 metres. His average speed on this race was 10.44 m/s.

It took him 19.19 seconds to run 200 metres. His average speed on this race was 10.42 m/s. You can say, Usain ran slightly faster in the 100m sprint.

For more information, formulas and other conversions you can use our free Speed Converter.