What component of the initial velocity is responsible for the maximum height reached by a projectile?

Vertical velocity. The maximum height reached by a projectile is determined by its vertical velocity, specifically the initial upward velocity imparted to the object when it is launched. The greater the upward or positive vertical velocity at the start, the higher the maximum height the projectile will attain. As the object travels upward, gravity acts to slow its ascent until it momentarily stops at its maximum height before beginning its descent. In contrast, the horizontal velocity does not affect the maximum height, as it only influences how far the object will travel horizontally during its flight. The total velocity, which combines the horizontal and vertical components, is also not directly responsible for determining the maximum height achieved by the projectile.