I didn't have much trouble with the 1-D 1 object kinematics, but I'm having a lot of trouble with 2 objects. I'd just like some help setting the problem up: Two stones are dropped from the edge of a 60m cliff, the second stone 1.6s after the first. How far below the top of the cliff is the second stone when the seperation between the two stones is 36m? I thought the best way to set this up would be: X = Displacement of first stone in terms of a Y = Displacement of second stone in terms of a X-Y=36m (vt+.5at2)-(vt+.5at2)=36 (Pretend I have subscripts to indicate they aren't the same variables and don't cancel each other out right away.) I don't know if that's right, and even if it is, I just can't think of how to factor in the 1.6s. A little guidance on how to get started would be appreciated.