Gravity is a force of attraction that exists among all objects. Every object attracts every other object. Most objects are too small for their gravitational force to be measured or even noticed. Because the earth is large, its gravitational force is very strong. Gravity holds things on Earth's surface as it draws everything toward the center of the planet. Suppose that a very narrow tunnel has been drilled straight through Earth's center as shown in the diagram. What will the marble MOST LIKELY do if it is dropped into the tunnel?

Explanation

Until the marble reaches Earth's center, gravitational force will continue to accelerate it. As it passes Earth's center, gravitational force will start to slow its motion and it will head toward the other side. If this experiment could actually be done, the marble would oscillate from one side of Earth to the other with the marble reaching its maximum speed at Earth's center and having practically no speed as it reached each surface point.

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