School bus safety has been a hot issue of social concern in recent years, and the hidden dangers are mainly speeding and overloading. The ninth grade math activity group of a middle school conducted an experiment to test the speed of cars, as shown in the figure. First, choose a point A next to the straight highway L, and then determine a point on the highway, thus measuring the rice. It is known that when the speed limit of the school bus is 50 kilometers, if the measured AD is 40 meters, a school bus will travel at a constant speed in seconds. Please explain.

Classmates, the above questions are the original questions I found on the website for answers. Here is the answer address/exercise/math /269 134. I believe you will understand after reading the answer. Come on! Otherwise, I can give you a screenshot.