Question: a ball thrown vertically upward reaches a certain height and comes down again. What can you say about its kinetic energy at the maximum height?
Answer: Kinetic energy at the maximum height is Zero.
The vertically upward-moving ball actually has a retardation of motion during its upward movement, because gravity continuously pulls it downwards (opposite to the direction of motion).
As a result, its velocity falls as it moves upwards.
And at the highest point of its motion, the velocity of the ball becomes zero. velocity v = 0.
Hence, the Kinetic energy of the ball at the maximum height KE = (1/2)mv2 = 0.
Read more: Vertical Motion Physics