Here's why:
* Vertical motion: When a ball is thrown upwards, gravity acts on it, constantly slowing it down.
* Maximum altitude: The maximum altitude is the point where the ball momentarily stops moving upwards before it starts falling back down.
* Zero velocity: At this point, the ball's upward velocity has been completely reduced to zero.
Think of it like a car coming to a stop at a red light. The car has been moving but reaches a velocity of zero when it stops. The same principle applies to the ball at its maximum altitude.
