Question

The speed of a moving car is 72 km/h. Calculate its speed in m/s.

Answer 1

Hint: we are asked to convert the given value of speed in km/h to m/s. To convert this we need to know the value of 1 kilometer in meters and the value of 1 hour in seconds. Knowing this we can convert km/h into m/s.

Complete step-by-step answer:
In the question we are given a car which is moving with a speed of 72 km/h.
We are asked to calculate the car’s speed in m/s.
We know that 1 kilometer is 1000 m.
Hence to convert kilometers into meters we need to multiply the value in kilometers with 1000.
We also know that 1 hour is 60 minutes and 60 minutes is $60\times 60=3600\sec $. Hence to convert hour to meter we need to multiply the value in hour with 3600.
Therefore to convert km/h into m/s we need to multiply the value in km/h with $\dfrac{1000}{3600}$.
Thus in this case we have the speed of the car as, 72 km/h.
Therefore to calculate the speed in m/s we need to multiply 72 km/h with $\dfrac{1000}{3600}$.
 i.e. $72km/h=72\times \dfrac{1000}{3600}$
$\Rightarrow 72km/h=20m/s.$
Hence the speed of the car in m/s is 20.

Note: Here we multiply the value in km/h with $\dfrac{1000}{3600}$.
We know that $\dfrac{1000}{3600}$ can be simplified into $\dfrac{5}{18}$.
Therefore instead of multiplying the given value in km/h with $\dfrac{1000}{3600}$ we can simply multiply that value with $\dfrac{5}{18}$.
By doing this also we get the same solution.
Considering the given case in this form, we can write
$72km/h=72\times \dfrac{5}{18}$
$\Rightarrow 72km/h=20m/s$.
Hence by multiplying with $\dfrac{5}{18}$ also we can convert km/h into m/s.