Question

Why is it not necessary for a body following another to atop to avoid collision?

Answer 1

Answer:

Well lets say both the bodies are moving with some velocites and are separated by some distance.  

If the body thats already ahead has a velocity which is equal to or more than the velocity of the body following it, then it will always remain ahead.  

So despite the body thats  following, never ceasing to move,  it will never be able to catch and hence never collide.

Explanation: