Need help understanding RC Kaboom Show on Codeforces

This problem was part of Codeforces Educational Round 88.

Problem Link:

I just cannot understand what the editorial is saying. I could only understand how to calculate the velocity vectors.

After that it is a total blank. How is sweep line used ? How are different launch times used ? Where does binary search fit in ?

The editorial can be found here: (Problem F)

How am I suppose to calculate different cars launched at different times ? It would be easier if it just said they were all launched at the same time but the examples shows we can launch them at different times.

Any help would be helpful.

Especially if you could tell me the pre-requisites for the problem, or if there are any easier problems available.