Final answer:
Gravity is the attractive force between all masses and acts universally. Newton's law of gravitation states that the force depends on the mass of the objects and the distance between them. The size of the objects, in terms of mass, is crucial to the strength of the gravitational pull, explaining why Earth's gravity dominates our daily experiences.
Step-by-step explanation:
To respond to each student's comment on gravity:
Student A is partially correct in saying gravity pulls “stuff” down, but it's important to clarify that this “down” direction refers to the pull of gravity towards the center of a massive body such as Earth. It's not just “down” in a universal sense, but towards the center of mass of an object.
Student B has a more accurate description, stating that gravity is an attractive force that exists between all objects that have mass. Indeed, gravity is universal and acts between any two pieces of matter in the universe, no matter how far apart they are.
Student C raises a question about why all objects don't clump together if gravity is always attractive. While it is true that everything with mass attracts everything else, the effect is much weaker with greater distances. Additionally, other forces and the initial motion of objects can prevent them from clumping together. For example, planets orbit the Sun instead of crashing into it because they have forward momentum that balances the sun’s gravitational pull.
Student D is on the right track in considering the size of the objects (or more accurately, their mass).
Newton's universal law of gravitation states that every particle in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. This also explains why an object like Earth has a much stronger gravitational effect on us than a smaller object, such as an apple.
Gravity is a fundamental force that is essential to our understanding of the universe. It keeps planets in orbit, gives us weight, and explains why objects fall to the ground when dropped. Despite its universality, gravity is the weakest of the fundamental forces and can be overcome by other forces, such as electromagnetism in the case of a magnet lifting an iron nail against the pull of Earth's gravity.