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

km/h to m/s - unit conversion from kilometer/hour to meter/second
figure 1: km/h to m/s – unit conversion from kilometer/hour to meter/second and vice versa

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.

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

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