Chapter 6

What is the glue that keeps the Moon bound to the Earth?

• Gravity

• Astronomical Units

• Center of Mass

• Nuclear Force

What is true about Gravity?

• It is always repulsive, never attractive.

• Can be both attractive and repulsive, near the poles

• It is always attractive, never repulsive.

• Cannot be neither attractive and repulsive, near the poles

The strength of the gravitational force between two objects depends only on

       1) how ___ they are.

       2) how ___ they are.

• Bright/Wide

• Massive/Wide

• Bright/Far

• Massive/Far

What is the eventual result of an unstable system with no initial velocity?

• The objects will collide with one another.

• A stable system.

• The objects will repulse away from one another.

• A disk like system.

In a binary star system, the more massive object ___

• Spins slower and orbits around the smaller object

• Lies closer to the center of mass and always traces a smaller ellipse than the less massive one

• Spins faster and orbits around the smaller object

• Lies farther from the center of mass and always traces a bigger ellipse than the less massive one

Why do we assume that the more massive object in a binary system moves slower?

• Larger = Slower

• Being closer to the center of mass and having the same orbital period.

• Smaller = Faster

• The pull of gravity creates a slowing tension.

Where is the common center of mass located for the Earth and the Moon?

• Inside the Earth

• The exact center

• Inside the Moon

• More towards the Earth but still outside

Using the Mass Ratio, where is the center of mass for a binary system where one object 5 times more massive than the other.

• 4/6

• 2/4

• 3/5

• 1/3

How long does it take for the moon to complete one rotation

• 30 days

• 20 days

• 27 days

• 31 days

What is synchronous rotation?

• Moon always shows the same face to Earth

• The moon revolves around the earth in 365 days

• Moon rarely shows the same face to Earth

• The moon revolves around the sun in 365 days