Want to know how fast something is? How quickly it moves and how long it will take to get somewhere? If you know the speed then you can.
In metric, speed is usually measured in kilometres per hour. The kilometre is a unit of length. Another unit of length, the metre, can be also be used as the basis for speed, as in metres per second. The symbol for kilometres per hour is km/h, and the symbol for metres per second is m/s. Metres per second are mostly used for more scientific usage, and we really only need to worry about km/h here, although it is interesting to note that average human walking speed is around 1 metre per second, which makes it very easy to remember, equivalent to 3.6 km/h — multiply metres per second by 3.6 to get kilometres per hour, or divide km/h by 3.6 to get m/s.
Here are some example speeds:
Stationary objects, not moving,
1 m/s, 3.6 km/h
Average human walking speed
Easy cycling speed on a bicycle
Typical car speed on residential roads or busy city roads
Vehicle on main road, travelling reasonably fast
Fast car on motorway, typical speed of a cheetah running, freight trains
High speed train
Airliner cruising speed
The speed of sound at sea level on Earth (it varies according to altitude, air pressure, and in space the speed is zero), also known as Mach 1
Current world land speed record, held by the ThrustSSC car (Mach 1.016)
The fastest speed recorded by the Concorde aircraft in 1996
1000 m/s, 3600 km/h
Speed of a bullet from a rifle
26 000 km/h
Re-entry speed of the space shuttle
40 320 km/h
Earth’s escape velocity
299 792 458 m/s, 1 079 252 849 km/h
The speed of light, which we can approximate to 300 million metres per second, or 1 billion kilometres per hour
We can measure wind speeds in kilometres per hour. The chart below shows us what various wind speeds relate to in terms of calm, hurricane, etc.