The initial odometer reading of a car is 369 km. It travelled for 2 hours and the final odometer reading showed 469 km. Find the approximate average speed of the cab.

CONCEPT:

• Average speed: The total path length travelled divided by the total time interval during which the motion has taken place is called the average speed of the particle.

\(Average\;speed\;\left( {\bar v} \right) = \frac{{total\;path\;length\;\left( S \right)}}{{total\;time\;taken\;\left( t \right)}}\)

​EXPLANATION:

Given -  Initial odometer reading (s₁) = 369 km,  final odometer reading (s₂) = 469 km, and Time (t) = 2 hour

• Mathematically Average speed is written as

\(\Rightarrow v = \frac{\Delta s}{t}=\frac{469-369}{2}=50\,km/hr\)

• To convert the km/hr to m/s, multiply km/hr by 5/18, therefore  

\(\Rightarrow v = 50\times \frac{5}{18}\approx14\, m/s\)

NOTE:

• Odometer or odograph: It is a device used to measure the distance travelled by the vehicle.
• Speedometer or speed meter: A device used by the vehicle to measure the speed of the vehicle.