What happens to the vertical velocity of an object as it travels through the air?

When an object is launched into the air, it initially has a high vertical velocity. As it ascends, the vertical velocity decreases due to the force of gravity acting against the direction of motion. At the peak of its trajectory, the vertical velocity is zero for a brief moment. As the object begins to descend, the vertical velocity increases again, but in the opposite direction. This is because gravity is now acting in the same direction as the motion. The object continues to accelerate until it hits the ground, at which point the vertical velocity is again zero.