A missile was to be launched at an angle 15 degree to the horizontal with an initial velocity to hit a target 300m away. Calculate initial velocity and the maximum height

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.