A ball is thrown straight up into the air. At each of the following

instants, is the magnitude of the ball’s acceleration greater than g,

equal to g, less than g, or 0? Explain.

a. Just after leaving your hand.

b. At the very top (maximum height).

c. Just before hitting the ground.

If there is no other influence on a ball that is thrown upwards then the ball will move with a decreasing velocity and the acceleration remains constant.

When a ball is thrown upwards, it has a positive velocity soon after it is leaving the hand. If we consider that there is no air resistance (which has a negligible influence on gravitation) then the ball should have an acceleration equal to the acceleration of gravity g.

At the topmost position, the speed of the ball becomes zero.

The speed of the ball gradually becomes zero at a peak point. As the influence of the earth on the ball is still the same and always remains constant, the acceleration of the ball at that point will be same as g.

After reaching a certain height, the ball comes back to the ground. We have to discuss if the acceleration of the ball gets increased, reduced or remain the same.

When the ball starts moving down the ground, still the acceleration remains constant as there is no air resistance on it mentioned in the question. Foe free fall, the acceleration is equal to the acceleration of gravity (g). So just before the ball hits the ground, its acceleration remains the same i.e. gravitational acceleration g.