Final answer:
The velocity and initial velocity are important when throwing a baseball directly upward.
Step-by-step explanation:
The subject of this question is Physics. When you throw a baseball directly upward, the velocity and initial velocity are key concepts to consider.
The velocity is the rate at which the baseball is moving in a given direction. When you throw the baseball upward, its velocity starts decreasing until it reaches its highest point, then it starts to decrease again as it falls back down.
The initial velocity is the velocity of the baseball at the moment it is released. In this case, it would be the velocity of the baseball when it leaves your hand and starts moving upward.