Question

A stone is thrown vertically upward at a speed of 39.80 m/s at time t=0. A second stone is thrown upward with the same speed 2.890 seconds later. At what time are the two stones at the same height?

Answer 1

Find where the 1st stone is when the 2nd is thrown, this way you can eliminate the time difference. Use their equations of motion to find the time where they are the same point in space.