Solutions to homework 2.

1. List 9 objects in the solar system, three each with gaseous, icy and rocky surface.
Gaseous: The Sun, Jupiter, Saturn, Uranus, Neptune.
Icy : Europa, Ganymede, Titon, Triton, Comets, Pluto.
Rocky : Mercury, Venus, Earth, Mars, asteroids, meteorites, most moons.

Note: The above categories are for the objects' surfaces.
Interiors can be different.

2. If there is a solar eclipes today, when is the next possible eclipse?
Why might there not be an eclipse at that time?
*** 2 weeks, and it will be an eclipse of the other type.
A tilt of the moons orbtal plane often keeps this from happening.

notes & sketch

3. Give one example each for each of Newton's laws of motion.

***1. Objects in motion tend to stay in motion. E.g. air hockey pucks.

***2. F=ma. Forces of friction cause moving things to stop.
Takes more force to accelerate a larger mass.

***3. Action/opposite reaction balance.
As you stand on floor you push down on it with your weight, and the floor pressure pushes up.
They are equal in magnitude but opposite in direction, thus cancelling.
If they were not equal, you would accelerate (a=F/m).



4. When standing on the Moon, an astronaut dropped a feather and a rock
from the same height. Both hit the surface at the same time. Can you
explain this using Newton's second law of motion, and his law of gravity?
notes & sketch:part1
notes & sketch:part2

5. Make a list of at least 10 ``key words" with special definitions in astonomy.
Give a very short definition of each.

*** Answers can of course vary on this. Make sure you understand the definitions!


6. How is the inside of the sun different form the surface?
*** The inside is hotter, denser, with more pressure and
the gas is more highly ionized (all these three are related).
Also, the ratio of He to H is more because about 50% of the
original H in the core (central 10% of radius) has been
converted by nucleur fusion to He.