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### Student Question

Secondary IV • 1yr.

How do we go from m/s to km/h and vice versa? Also, how do you convert velocities using position and time measurements?

Physics

## Explanations (1)

• Explanation from Alloprof

Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

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Team Alloprof • 1yr.

To carry out these conversions, it is always necessary to remember the speed formula::

v = ∆x / ∆t

Legend:

• v: speed of an object

• ∆x: variation of the position of an object

• ∆t: variation time

To find the speed of an object, you must always divide the distance traveled by the object by its variation in time. The unit resulting from this calculation will be the unit used to measure the distance traveled in the numerator's spot, and the unit used to measure time as the denominator. For example, if a mobile moves 8 meters in 2 seconds, the speed will be:

8m / 2m = 4 m/s

To convert m / s to km / h, we must remember the speed calculation, but also the conversions of units in general:

• 1 km = 1000 m

• 1 h = 60 minutes • 60 s / minute = 3600 seconds

In short, when we want to convert m / s into km / h, we use these ratios:

X m/s = Y m/s • ((3600s)/h) / ((1000m)/km) = Y(km/h)

It is the same principle, but conversely, when converting km / h into m / s:

Y km/h = X km/h • ((1000m)/km) / (3600s)/h)) = X(m/s)

As per the conversion of position and time measurements into speed ​​measurements, you must remember the speed formula. For example, you may begin by converting the units to have meters and seconds, or kilometers and hours, and then divide the distance measurement by the time measurement.

I hope you found my answer helpful, do not hesitate if you have other questions!