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.