![]() It is $-g$ when it leaves the hand, $-g$ when it stops instantaneously at the top of its flight, and $-g$ when it hits the ground. Note that while it is in the air the acceleration of the ball remains the same even though the velocity changes. As soon as the ball leaves the thrower's hand, the only force acting on it is gravity, so its acceleration is $g$ downwards. ![]() At that point, the downward acceleration continues to cause the object to slow down, stop, and then fall.Īnswer $a$ is correct. That's Newton's 2nd Law.$$\vec$, downward. There are two forces (push of the hand and weight) which combine to give the actual, single acceleration. There is not an acceleration due to gravity and a separate acceleration due to the push of the hand. There is only one linear acceleration of the object. Does it instantaneously become zero, such that the ball only has an initial velocity upward but not an initial acceleration upward?įirst we need to clear up the concept of acceleration. However, that question and its answer does not address what happens to the upward acceleration from the hand. Then there is no force acting on the ball and it is moving at a constant velocity, but this doesn't make sense because the ball is certainly accelerating due to gravity.ĮDIT: It seems that according to the answer of another question here, "a" is correct. If b, at some point the only acceleration on the ball must be from gravity (because otherwise the ball would keep going forever like a rocket), yet this means the acceleration is decreasing and at some point it will be 0. If a, how it can be that the acceleration changes instantaneously to that of gravity, what happens to the acceleration from the throw? The instant the ball leaves the hand, what is its acceleration? ![]() Since the mass of the ball doesn't change, the acceleration upwards must be greater than the acceleration downwards for the upward force to be greater than the downward force. There must be some upward acceleration which is greater than the acceleration due to gravity, since in order for the ball to move, the upward force must be greater than the force of gravity. ![]() A ball sitting in a person's hand is at rest. ![]()
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