If Keiji is standing still on Earth and throws a ball straight up into the air, what happens to the ball after he releases it, and why? Provide a very brief response.
After Keiji releases the ball, it goes up for a moment but then it slows down, stops momentarily, and starts falling back toward the ground. Gravity is the force that pulls the ball back down. On Earth, gravity pulls objects toward the center of the planet. When Keiji throws the ball upwards, he is giving it energy to move against the force of gravity, but gravity is constantly acting to pull it back down. When the ball's upward motion energy is completely used up, the force of gravity takes over, causing it to decelerate until it reaches a stop, and then accelerates it back towards the ground.