When an object is thrown vertically upward from the surface of the earth: what is the instantaneous velocity in the point of maximum height? what is the acceleration in the point of maximum height?

zero, acceleration due to gravity = 9.8 m/s^2

Explanation:

When an object throws vertically upwards, the acceleration acting on the object is acceleration due to gravity which is acting in vertically downwards direction.

As the object moves upwards, its velocity goes on decreasing because the direction of velocity and the acceleration both are opposite to each other. At maximum height, the velocity of object becomes zero and then object starts moving in downwards direction.

Thus, the value of instantaneous velocity at maximum height is zero but the vale of acceleration is acceleration due to gravity which is acting vertically downward direction.

the independent variable, or the one that is intentionally manipulated is the speed.