distance = speed * time.
so the police car starts 40km from the cross-roads, the truck stars 30km away.
Can you use that information to find the displacement vector?
Problem reads: A truck is traveling due north at 30km/hr towards a crossroads. On a perpendicular road a police car is traveling west toward the intersection at 40km/hr. both vehicles will reach the crossroads in exactly one hour. find the vector representing the displacement of the truck with respect to the police car.
What I know: (maybe)
The vector is part of an isosceles triangle with 90° where the vectors meet and 45° where the vectors start.
What I don't know:
Since the truck travels at 30km/hr and takes one hour to reach the crossroads;
Distance from the crossroads to the truck=
Since the police car travels at 40km/hr and takes one hour to reach the crossroads;
Distance from the crossroads to the police car=
Please refer to the attached figure. You will see that the resultant vector representing the displacement is 30 km in length and directed from east to north by an angle of 36.9 degrees.
Hope you understood.