Chapter 4, Problem 3A

Does the speedometer of a car read instantaneous speed or average speed?

Solution

To identify: Whether the speedometer of a car read instantaneous speed or average speed.

Introduction:

Average speed is the ratio of total distance traveled to total time. While the instantaneous speed is the magnitude of instantaneous velocity at a particular time. Mathematically, it is given as,

  $s_i=\frac{ds}{st}$

Where,

ds is the distance.

dt is time interval.

Explanation:

Speedometer is a gauge that measures and displays the instantaneous speed. This means it will show the speed of a car at a particular instant.

Since, speed is the ratio of distance over time. So, to calculate the instantaneous speed a very small instant of time is considered.

Conclusion:

Therefore, speedometer of a car reads instantaneous speed.