2 automobiles each of mas 100kg, are moving at the same speed, 20m/s, when they collide and stick together.?

Question

in what direction and at what speed does the wreckage move a) if one car is driving north and the other south? b) if one car was driving nirth and the other east?

Now i have the first answer to A but i dont know how to get the second answer because i dont know what the triangle effect is. so if anyone could explain the second answer to me without mentioning the triangle effect please do so, so i can understand this problem.

Thanx!

Answer 1

Define a coordinate system where ne is like x and nw is like y. Then both cars have a component of their velocity in the ne direction equal to
Vne = 20 m/s sin 45

One car has a nw component
Vnw = 20 m/s sin 45
The other car has a nw component
Vnw = -20 m/s sin 45

The cars' components in the nw direction will cancel out. The cars' components in the ne direction will both be equal, so they will happily carry on in that direction at that velocity:
Vne = 20 m/s sin 45