If Keiji stands at the base of a hill and throws a ball straight up into the air, what will happen to the ball after he releases it, and why? Provide a very brief response.
After Keiji releases the ball, it will initially move upward, then slow down until it stops momentarily, and finally it will reverse direction, coming back down the hill towards him. This happens because when Keiji throws the ball upwards, it has kinetic energy that propels it against the pull of gravity. As the ball rises, gravity slows it down, reducing its upward speed until it reaches a point where its upward velocity is zero. At this highest point, the force of gravity then pulls the ball downward, accelerating it back toward the ground. If he threw it exactly straight up and no other forces act on it (like wind), it will return along the same path it went up and will fall back to the ground near where Keiji is standing.