A student bounces a tennis ball. She drops the ball, and then it bounces back up to her. When does the ball have zero kinetic energy?(1 point)
Responses
As soon as she drops it
As soon as she drops it
At the very top of its bounce
At the very top of its bounce
Exactly when it hits the ground
Exactly when it hits the ground
Just after it hits the ground
At the very top of its bounce
The ball has zero kinetic energy at the very top of its bounce.
The correct answer is "At the very top of its bounce."
To understand why, let's first define what kinetic energy is. Kinetic energy is the energy an object possesses due to its motion. It depends on an object's mass and its velocity. When an object is at rest or not in motion, it has zero kinetic energy.
When the student drops the tennis ball, it begins to accelerate downwards due to the force of gravity. As it accelerates, its velocity increases, resulting in an increase in kinetic energy. At the very moment it hits the ground, the ball has its maximum velocity and, therefore, its maximum kinetic energy.
However, as the ball starts to bounce back up, its velocity decreases and eventually becomes zero at the very top of its bounce. At this point, the ball momentarily comes to a stop before changing direction and falling back down. During this momentary stop, the ball has zero velocity and, consequently, zero kinetic energy.
Therefore, the correct answer is that the ball has zero kinetic energy at the very top of its bounce.