Answer:
Explanation:
The rock will decelerate at the rate of g or 9.8 m sâťÂ˛while on its way up because of gravitational attraction towards the earth.  . In other words , it will accelerate with the magnitude - 9.8 m sâťÂ˛ while on its way up.
On its way down , it will accelerate due to gravitational attraction. In this case acceleration will be positive and equal to 9.8 m sâťÂ˛.
At the highest point in its trajectory , rock  becomes stationary or comes to  rest momentarily. So at the peak position , velocity is zero.
At the highest point , as the gravitational force continues to act on the body undiminished, its acceleration will remain the same ie 9.8 m sâťÂ˛ at the highest point as well. It will act in the downward direction.