ch12_awks

  Chapter 12 Review

Issac Newton witnessed a falling apple from a tree. The apple was later used for Newton's theory on gravitational attraction. He hypothesized that there was a gravitational attraction between every pair of objects no matter their size or distance. www.fleursdumall.blogspot.com
 * The Falling Apple: **

The moon should continue to move in a straight line theoretically with the absence of an external force. The moon, however, does not travel in a straight line but instead orbits the Earth. This happens because some force is acting on the moon to keep it orbiting the Earth; this force is gravitational attraction. The moon falls toward the Earth a very small amount every second relative to the path it would travel if it was moving in a straight line. The distance the moon falls every second is about 1.4mm every second. The moon falls around the Earth, but the Earth and every other planet falls around the sun. If for any reason the Earth or any other planet stopped moving for even a second the planet would fall straight to the sun. One of the biggest reasons why the moon doesnt fall into the earth is because of tangential velocity because it ensures circular motion around the earth. [|www.fallingpixel.com] Newton's Law of Universal Gravitation: ** Newton discovered that every single piece of matter in the universe, no matter what the size or distance, attracts each other. He also discovered that this was because of the universal force called gravitational attraction. The equation for finding the gravitational attraction is Fg=G(m1m2)/r^2. Masses of the two objects is m1 and m2. The distance between them is r. Where G=6.673*10^-11(N*M^2/kg^2). The greater the masses, the greater the force is. The greater the distance, the smaller the force is. www.physics.mun.ca
 * The Falling Moon and Earth: **

Since the denominator above includes the square of the distance gravity it is said to follow **the inverse square law.** If the distance between the two objects increases, the force of attraction will decrease by the square of the amount the distance increased. Gravitation decreases according to the inverse square law. The force of gravity weakens as the distance squared.
 * Gravity and Distance: **

Since every object in the universe is attracted to another object this led to the discovery of the planet Neptune. It was discovered because of hte attraction between Neptune and Uranus. This same thing happened to lead to the discovery of Pluto. www.worldbook.com  Important Vocabulary:
 * Universal Gravitation: **
 * Law of universal gravitation**: states that every object attracts every other object with a force that for any two objects is directly proportional to the mass of each object. The greater the masses, the greater force of attraction between them.
 * Inverse square law**:A physical quantity varies inversely as another quantity squared.
 * Tangential Velocity**:component of velocity tangent to the trajectory of a projectile.
 * Perturbation**: the changing of a planet's tradition orbit due to the influence of gravitational forces.