Two boys, X and Y, decide to measure the speed of some of the vehicles travelling along a road.
The two boys stand 405 m apart beside the road, as shown in Fig. 1.1.
Boy X has a stopwatch which he sets to zero. As a vehicle passes boy Y, boy Y drops his hand
as a signal to boy X to start his stopwatch. Boy X then stops the stopwatch as the vehicle
goes past him.
The appearance of the stopwatch is then as shown in Fig. 1.2.
How long did it take for the vehicle to travel from Y to X?
time = ............................................... s