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**Fratricide** **A man at the top of a building 20m high releases a stone from rest; 0.60 seconds later he throws a marble vertically downwards with an initial velocity of 8.0 ms**^{-1}. How long after the stone was dropped does the marble pass the stone?

I know that after 0.6 seconds the stone is travelling at 6 ms^{-1}, and because the acceleration is constant, this means that the marble is always travelling 2 ms^{-1} faster than the stone. I'm thinking that I need to make equations for the distance of each object, equate them and solve for* t, *but I can't seem to get started. If you could point me in the right direction, that would be great.