So if I have two exactly the same rocks and drop one then the other 2 seconds later, how would I find the distance between the two rocks when the first hits the ground? I know the height, let's say it's 40m. I want to know HOW to do this. Would I find time it takes the rocks to hit the ground first since both are the same? Then set each equal? Mostly just having issues with what equations I suppose

  • $\begingroup$ Hint: use $S_y = u_yt - 1/2gt^2$ $\endgroup$
    – xasthor
    Feb 14, 2017 at 7:03

1 Answer 1


Find the time it takes for the first rock to hit the ground using your constant acceleration formulas and then sub this time -2 seconds back into your formula to find the position of the second rock at that time.

  • $\begingroup$ Does this work though? That's what I was thinking but is it true considering distance between increases in free fall, therefore is it still 2 seconds behind when the first hits the ground? $\endgroup$
    – Mad
    Feb 14, 2017 at 1:08
  • $\begingroup$ I believe you'll find your answer here: physicsforums.com/threads/… $\endgroup$ Feb 14, 2017 at 13:52
  • $\begingroup$ As EOC suggests, do the calculation, find an answer, ask yourself if it is reasonable, then decide if the procedure works. If you are always making excuses not to do a calculation, you will never gain confidence in your own abilities. $\endgroup$ Feb 14, 2017 at 18:05

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