Universal Gravitation Applied Science Mr. Kuffer

The Fundamental Force! The gravitational force is weak, but very long ranged. Furthermore, it is always attractive, and acts between any two pieces of matter in the Universe since mass is its source.

The Tortoise and the Hare: Gravity Always Wins Why Gravity is the Most Important force: –it is long-ranged and thus can act over cosmological distances, and –it always supplies an attractive force between any two pieces of matter in the Universe. Thus, although gravitation is extremely weak, it always wins over cosmological distances and therefore is important to understanding our Universe.

Universal Gravitation We’ve all heard the story… An apple falls on Isaac Newton’s head He understands Galileo’s idea of inertia… Objects at rest will… Therefore there must be some force acting on the apple… The problem he runs into is… –What is causing the force?

What is causing the force? This led to the “most far-reaching generalization of the human mind” Newton applied what he knew about the apple to attempt (successfully) to explain the motion of the moon around the Earth.

The Falling Moon? Why doesn’t the moon just remain in motion? A: Something is pulling it in… F c ! The moon is “falling around the Earth just as the apple…okay, not quite “just as” the apple… but similar.

Visualize it! Newton says “Object in motion… Can you see that the force exerted by the Earth causes the moon to fall “below” the straight line that it would have traveled?

The Falling Moon! The moon “falling” is a bit different then the apple falling. The moon falls beneath that straight line. We say it falls “around” the earth. Let me explain… What are the odds? Gotta get it just right, Wow!

You See? The moon is just a projectile that wants to stay in motion but ends up circling the earth b/c of gravity (which provides the F c ). Likewise, the earth is just a projectile circling the sun b/c of gravity. (confirming the Copernican theory that the sun, not the earth was the center of the solar system)

Newton’s Law of Universal Gravitation. Every object attracts every other object with a force that for any two objects is directly proportional to the mass of each object. (that means it depends on the masses involved) He also noted that it depends on the separation between the masses. The further away, the less attraction F~ m 1 m 2 / d 2

Newton’s Law of Universal Gravitation. If this is true, then isn’t there an attraction between all object? After all, all objects have mass. A: YES, but the forces between these masses are often negligible, b/c their masses are so small in comparison to the earth.

The BIG bang or the BIG crunch? Food for Thought?! According to gravitational concepts, what goes up…. Apply this to the universe and… The presently expanding universe (like a stone thrown upward) will eventually collapse (like the stone returning, due to gravity), or will it? Hmmmmm?

In Summary Gravitational concepts are present not only on earth, but throughout the universe. Orbiting objects (like the moon) are actually falling around another object (like the earth). Everything pulls on everything else with a force that depends on the masses and the distance between the masses. –The greater the mass, the greater the force –The greater the distance, the smaller the force F = G (m 1 m 2 / d 2 )