Kilometer per hour (km/h)

Definition

The kilometer per hour (km/h) is a unit of speed expressing the distance traveled in kilometers over one hour. It is part of the International System of Units (SI) and is defined as 1 km/h = 1,000 meters/3,600 seconds.

History

The use of kilometers as a measure of distance started in the early 19th century with the metric system's adoption in France in 1795. The concept of speed in km/h gained prominence in the 20th century, especially with the rise of motor vehicles.

Uses

Kilometers per hour is commonly used in road traffic speed limits and vehicle speedometers in most countries, particularly those using the metric system. It is also used in various scientific fields and engineering applications to measure speed.

Conversions

  • 1 km/h = 0.27778 m/s
  • 1 km/h = 0.621371 mph
  • 1 km/h = 1,000/3,600 m/s (exact)

Fun Facts

  • A common misconception is that km/h and mph can be directly compared without conversion; they are different units.
  • Countries like the U.S. primarily use miles per hour (mph), while most others use km/h for speed measurement.
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