High School Physics

# km/h to m/s – unit conversion from kilometer/hour to meter/second

Last updated on April 19th, 2023 at 03:47 pm

Km/h to m/s or km/hr to m/s conversion: To convert km/hr value to m/s value just multiply the km/hr value with 5/18 and get the value in m/s. As example, 36 km/hr = 36 * (5/18) m/s = 10 m/s.

So, for this unit conversion from kilometer/hour to meter/second, you need to remember the conversion factor as 5/18 or (1/3.6)

Similarly, if you want to convert the unit from m/s to kilometer/hr, then the conversion factor is 18/5 or 3.6.

We can refer to this diagram as a quick reckoner. Here, Km means Kilometer and h or hr means Hour. So Km/h is kilometer per hour.
Similarly, m/s means meter per second which is the unit of speed in SI.

## How do we get this conversion factor’s value?

Just converting km and hour to meter and second respectively (taking to SI units).
Just see:
1 Km/Hr = 1000 m/3600 sec = 5/18 m/s
Thus we get the conversion factor 5/18 if we want to convert a value from km/hr to m/s.

## why do we need to do this conversion?

While solving numerical problems in Physics we mostly use the SI unit system and in SI the unit of speed is meter/second which is written as m/s. Now if the data is given in different units we need to convert those to SI first. Often we find speed data or magnitude of velocity is given in Km/hr. In these scenarios, we have to convert those to m/s. Hence this quick conversion is required.

See also  Multiples and Prefixes for Metric Units

## Problem with solution

1 ) A car is moving at a speed of 90 km/hr. What is its speed in SI?

Solution:
Speed v = 90 km/hr = 90 * (5/18) m/s = 25 m/s
So the speed of the car in SI is 25 meter/second

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