Question

90 km per hour is same as
A. 50 m/sec
B. 25 m/sec
C. 25 m/min
D. 50 m/min

Answer 1

Hint: From the above question and based on options, it is clear that we need to convert kilometers to meters and hours to seconds or minutes. So we need to know the conversions of length and conversions of time. So, we need to convert 90 kilometers per hour into meters per second or meters per hour.

Complete step-by-step answer:
Given, 90 kilometers / hour
Definition of speed: Measured as distance traveled per unit of time.
Definition of Kilometer: A kilometer (km) is a decimal multiple of the meter, the international standard unit of length, approximately equivalent to 39370.07 inches. A kilometer is now used officially for expressing distances between two places or points.
Definition of meters: A meter (m) is the base unit of length in the International System of Units (SI).
Therefore, 1km = 1000 meters
$ \Rightarrow $1 meter = $\dfrac{{1{\text{ km}}}}{{1000}}$
Definition of Hour: A period of time equal to 60 minutes that is 3600 seconds.
Definition of second: It is measured as the smallest unit of time.
$ \Rightarrow $1 second =$\dfrac{{1{\text{ hr}}}}{{3600}}$
Now, 90 kilometers per hour need to be converted to meters per second or minute.
Let x be 90 kilometers per hour which is needed to convert into meters per second
$ \Rightarrow $${\text{x = 90}}\dfrac{{{\text{km}}}}{{{\text{hr}}}}$
$ \Rightarrow 90\dfrac{{1000{\text{ m}}}}{{3600\sec }}$
$ \Rightarrow \dfrac{{90 \times 1000}}{{3600}}\dfrac{{\text{m}}}{{{\text{sec}}}}$$ = 25\dfrac{{\text{m}}}{{\sec }}$
Therefore, 90 kilometers per hour is equal to 25 meters per seconds

Note: If the problem was given to convert kilometers to meters, there is a standard equation for this type of conversion. To convert a Kilometer per hour into a meter per second, we need to multiply by 5 and then divide it by 18. This standard form got from this $\dfrac{{\dfrac{{1{\text{ km}}}}{{1000}}}}{{\dfrac{{1{\text{ hr}}}}{{3600}}}}$fraction which we used in the solution to solve. When we solve this fraction we will get the above form.