Achild drops a ball from a window. the ball strikes the ground in 3.0seconds. what is the velocity if the ball the instant before it hits the ground

Explanation:

As we know that the ball is dropped from rest

So here we know acceleration of the object is due to gravity

So we will have

now we have

here we have

now from above equation we have

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.