Aball is thrown vertically upward. what is its instantaneous speed at its maximum height?

The instantaneous speed that its maximum height is zero.The reason is that the ball can only have potential energy while it is ascending vertically upward at the top of the height where the ball was thrown the speed decreases until it reached the peak and turn the speed into zero. However, as the ball falls off the potential energy is turned into kinetic energy. This time the kinetic energy will give the ball an increasing speed downward.

When you are making a guess you are forming a hypothesis