Quiz 3

Suppose that a planet of the same mass as Earth were orbiting the Sun at a distance of 10 AU. The gravitational force on this planet due to the Sun would be

1/100 of the gravitational force the Sun exerts on Earth.

The rotation period of the Moon on its axis with respect to space (its absolute rotation) is

27.3 days, the sidereal revolution period.

During a total lunar eclipse (as viewed from Earth) you are standing on the Moon looking back at Earth. What do you see?

Earth appears as a black disk with only a faint reddish glow around the edges.

Does the Sun or the Moon have a greater effect in causing the tides on Earth?

The Moon, because it has a larger difference between pulling on the near side and pulling on the far side of Earth.

Tidal friction between the Earth and Moon causes the Moon to

c. gain orbital energy, and thus decrease its orbital speed

The phase of the Moon when the Sun and Moon are separated by 6 hours of right ascension is always

either first or third quarter.

The reason the Moon always keeps one face toward Earth is that

gravitational forces from Earth act on the tidal bulge of the Moon.

How much of the total surface of the Moon is illuminated by the Sun when it is at crescent phase?

half

If you were standing on the Moon with Earth in view, how much time would elapse between two successive "Earthrises"?

infinite time, because the Earth does not rise and set as seen from the Moon.

The Moon would not go through phases if

it took one year to go around Earth.

In 1 hour, the motion of the Moon across our sky as seen against the background of stars is (Hint: Through what angle around the sky does the Moon move in one month?)

its own diameter or 1/2°

If two massive bodies, initially held at rest in space, are released, then they will begin to

move toward one another.

If an observer on Earth sees the Moon to be full, than at the same time an observer on the Moon would see Earth to be at what phase?

new

During a total solar eclipse the Moon just covers the Sun as viewed from Earth. If you know both the diameter and distance of the Moon, what else can you determine from this information?

only the ratio of the Sun's diameter to its distance

The total phase of a particular solar eclipse can be seen

only within a specific narrow strip across Earth's surface.

A lunar eclipse does not occur at every full moon because

the plane of the Moon's orbit is at an angle to the plane of Earth's orbit.

Spring tides occur

twice a month, at full and new moon.

How many "tidal bulges" are there on Earth, due to the Moon's gravitational pull?

two, one facing (almost) directly toward the Moon and one facing (almost) directly away from the Moon

Which of the following is the correct sequence of appearances of Moon phases in the sky?

waxing crescent, first quarter, waxing gibbous, full moon

The concept of the Hill radius is used to describe the condition for which tidal forces

will unbind a satellite from a planet