Answer to Question #240891 in Physics for cindyappletonx

Question

A passenger wants to check the accuracy of the speedometer of the car.

The car is travelling at a constant speed.

The passenger has a stopwatch.

The lampposts are 40m apart.

Describe how the passenger could determine the speed of the car as accurately as possible.

Answer 1

The passenger can count enough lamppost gaps, say, 100, to get 4 km of displacement, measure the time required to pass these 4 km, and divide the distance by time. The greater the distance, the better. The straighter the road, the better.