Answer :
0m/s, when a projectile is at the top of a vertical ascent it has a velocity of 0 for an infinitesimally small amount of time before it begins to descend under the force of gravity.
The velocity of the object at the instant it reaches the top of its trajectory is zero.
Final velocity of an object at the top
The velocity of an object decreases as the object moves upwards and becomes zero at the maximum height. The velocity of the object increases as the object begins to move downwards and becomes before the object hits the ground.
Thus, the velocity of the object at the instant it reaches the top of its trajectory is zero.
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