15. A stone is dropped from a height of 49 m. Two seconds later, a similar stone is thrown downward from the same height. If the two
stones hit the ground at the same time, what was the approximate
initial velocity of the second stone?
(A) -15 m/s
(B) -25 m/s
(C) -35 m/s
(D) 45 m/s
(E) -55 m/s