A stone is dropped into a river from a bridge 125 m above the water. Another stone is thrown vertically down 1.00s after the front is dropped. The stones strike the water at the same time.
Which of these is the position time curve of the two stones as seen by a person who is standing directly below the point from where they are projected?
Stone 1 is at s = +125m at t = 0 at t = 5 s = 0m
Also its velocity is decreasing (or increasing in negative direction). Hence the graph.
Stone 2 is at s = 125 m till t = 1 sec and then its starts falling and coming towards the observer so is height is decreasing and at t = 5 sec it hits him in the head.