So, the correct answer is "e. the moment the ball comes to a complete rest". This is the point at which all the forces on the basketball are balanced, and it is in a state of equilibrium.
To determine at which point all the forces on the basketball are balanced, we need to consider the various stages of its motion. Let's go through each option step by step:
a. The moment the ball leaves Darryl's hand:
- At this point, there are forces acting on the basketball, including gravitational force (weight) pulling it downward and the force applied by Darryl's hand to throw it upward. These forces are not balanced because the ball is accelerating upward, so it's not in equilibrium.
b. The moment the ball touches the floor:
- When the ball touches the floor, it experiences the force of gravity pulling it downward and the normal force exerted by the floor pushing it upward. These two forces are balanced at this moment because the ball is not accelerating in either direction; it's momentarily at rest. However, it's important to note that these forces are balanced only for a brief moment during the bounce.
c. When the ball is in the air:
- While the ball is in the air after being thrown, it experiences the force of gravity acting downward. There is no opposing force in the vertical direction (upward) to balance it, so it is not in equilibrium while in the air.
d. When the ball starts falling downward before coming to rest:
- As the ball starts to descend after reaching its highest point in its trajectory, the force of gravity is acting downward. There is no upward force to balance it, so the ball is not in equilibrium during this phase.
e. The moment the ball comes to a complete rest:
- When the ball comes to a complete rest in the coach's hands, it is once again in equilibrium. At this point, the force of gravity is balanced by the force exerted by the coach's hands (contact force). The ball is not accelerating; it's at rest in both the horizontal and vertical directions.