Final answer:
The ball's velocity at its highest point, after Colton throws it vertically into the air, is 0 m/s because it has been decelerated to a stop by gravity before starting to fall back down. Option b is correct.
Step-by-step explanation:
When Colton throws a ball vertically into the air and it reaches its highest point at 4.5 meters above the ground, the velocity of the ball at that point is an important concept in kinematics, a branch of mechanics in physics.
At the apex of its trajectory, regardless of its initial velocity or the force with which it was thrown, the ball's velocity is momentarily 0 m/s. This is because gravity has decelerated the ball to a stop before it begins to fall back down. Thus, the correct answer to the question posed is b. 0 m/s.
The other options listed, such as a. − 9.81 m/s, c. 9.81 m/s, or d. 4.5 m/s, do not accurately represent the velocity of the ball at its highest point. This is because at the highest point of its trajectory, the ball briefly stops moving in the vertical direction before starting to fall back down. The velocity at the highest point is equal to zero due to the change in direction.