There is a lonely massive star standing almost fixed at some point in this universe. There is a small planet projected with some velocity in some direction near the star. Given the masses of the star and the planet and the velocity, can you find whether the planet will collide with the star? If yes, how? (Neglect the displacements of the star) One thing that I thought and later realised that it was wrong was this :- If the planet has a non-zero angular momentum initially, from the conservation of angular momentum, it will never collide, because if it did, it's angular momentum would become zero at the time of collision which is not possible. But I realised that it's angular momentum can remain non-zero during collision if it's velocity becomes infinite. So the problem is still not solved.