When a stone is thrown vertically upwards with some initial velocity. It will move up until it reaches a certain point, known as the maximum height for that stone. Afterwards, it will start falling back down towards ground due to the gravitational force, g and will finally come back to its original place.

When a stone is thrown vertically upward its velocity?

An object that is thrown vertically upwards decelerates under the earth's gravity. Its speed decreases until it attains a maximum height, where the velocity is zero.

When a stone is thrown vertically upward why does it fall down after reaching a height?

When the stone travelling vertically upwards, it is experiencing the retardation due to gravity. After reaching maximum height, the stone descends with zero initial velocity, accelerated downwards due to gravity and reaches the ground after time t'.