A fireworks rocket is launched vertically upward at 40 m/s. At the peak of its trajectory, it explodes into two equal-mass fragments. One reaches the ground t1= 2.51s after the explosion. When does the second reach the ground? t= ......?? logiclly, it is 2.51 s also ....but I don't know. so could you pls guys help with that out ??