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Explain Hydrostatic Equilibrium
The pressure is not constant throughout a planetary atmosphere. A balance (equilibrium) is maintained between the outward pressure force and the inward gravitational force.
General facts about Sun
- 1. It's a star, a ball of (mainly) Hydrogen gas.
- 2. 700,000 km in radius.
- 3. Generates heat and light through nuclear fusion.
- 4. Surface temp. 5800K, central temp. 15 million K.
- 5. Hydrostatic equilibrium maintained between pressure and gravity.
T or F: The orbits of the planets are elipses and lie in, or close to the eciptic plane.
Describe the problems with the Geocentric model of the universe
- 1. The stars moved around a fixed Earth.
- 2. Could not explain retrofrad motion or phases of Venus.
Hydrostatic Equilibrium equation?
Describe the Heliocentric model of the universe
- 1. Planets, including Earth, orbit the Sun.
- 2. Phases of Venus and retrograd motion coud be explained in this model.
State Newton's Univeral Law of Gravitation
Gravity is a force of attraction between all matter in the universe causing apples to fall from trees and the Moon to orbit the Earth.
Describe retrograd motion
- 1. Retrograde motion is when a planet appears to be moving backwards in it's orbit.
- 2. Copernicus reasoned that planets further away from the sun would move more slowly than closer ones. As a faster planet overtakes the Earth in their rotations, its motion against the stars, as seen from the Earth, reverses.
What is g=GM/R2?
The gravitational field at the planets surface.
For Earth, g=6.673*10-11 x 5.974*1024/(6.378*106)2
What can be determined from the following formula:
- 1. If two planets have the same density, the larger will have the higher surface gravity.
- 2. If two planets have the same radius, the denser planet will have the higher surface gravity.
Explain escape velocity
- 1. If a projectile is launched vertically upwards as the projectile climbs, the planets gravity slows it down. It's kinetic energy is converted to potential energy.
- 2. For an object to escape, the kinetic energy must equal potential energy.