Astronomy 101 – Test 3 Review, Fall 2015
See Old Test 2 Online
Chapter 2
Section 2.3
Know: all the phases of the moon, synchronous rotation, waxing, waning
Answer: What causes the phases of the moon?
In what order do the phases of the moon happen?
Where is the moon relative to the earth in each phase?
How long does it take to go through the phases?
Section 2.4
Know: Total, Partial and Annular Solar Eclipse, lunar eclipse
Answer: What causes solar/lunar eclipses? In what phase of the moon do they happen?
Why don’t we have eclipses every month?
What does the moon look like during a total lunar eclipse?
How much of the earth can see a single solar or lunar eclipse?
Chapter 3
Section 3.1
Words to Know: geocentric, heliocentric, Copernicus, Tycho, Kepler, semimajor axis, eccentricity, period
Be able to Answer:
Who first developed a heliocentric model of the universe?
What are Kepler’s 3 laws?
What shape is an orbit with an eccentricity of 0, 0.5, 1?
In what part of a planet’s orbit does it move fastest/slowest?
How does distance from the sun affect the time it takes a planet to orbit?
Section 3.2
Know: Galileo, Inertia
Answer: What did Galileo do?
What is the Law of Inertia?
Section 3.3
Know: Newton, acceleration
Answer:
What are Newton’s 3 laws?
What causes acceleration?
What happens to the force if you change the mass? Or acceleration?
Section 3.4
Know: Gravity, Newton’s Universal Law of Gravitation
Answer:
Why do two balls of different masses hit the ground at the same time?
What is weight?
Why is your weight different on the moon?
What does Newton’s Universal law of Gravitation say gravity depends on?
If two objects are moved closer together, how is the gravitational force affected?
Clicker Questions:
Chapter 2
1) Suppose you are standing on the side of the Moon that faces the Earth. How would earth appear to
move in the sky as the Moon made one revolution around Earth?
a. The Earth would not move at all.
b. The Earth would rise and set.
c. The Earth would move across the sky but not rise and set.
d. You could not see the Earth.
Answer: A
Explanation: The moon always has the same face to the earth, so earth would always look the same
from the moon. The earth would go though phases, but not move in the sky. The place where you stand
on the moon never rotates away from earth.
2) When the Moon appears to completely cover the Sun (a solar eclipse), the Moon must be at which
phase?
A) Full
B) New
C) First quarter
D) Last quarter
E) No particular phase
Answer: B
3) Which, if either, occurs more often?
a. Total eclipse of the Moon as seen from Earth.
b. Total eclipse of the Sun as seen from the Moon.
c. They are both just as common.
Answer: C
Explanation: Answers A and B are both describing events that occur when the Earth is between the sun
and the moon. When in doubt, draw it out!
4) The figure shows a planet’s orbit that obeys Kepler’s laws. However, not all of the shaded regions
have equal areas.
During which part of the planet’s orbit (A, B, C, or D) would the planet move with the greatest speed?
Answer: C
5) You read in the paper that a new planet was found. The article states that when it is closest to its star,
it moves at 31 km/s. When it is farthest from its star, it moves at 35 km/s. This story has an error
because:
a. Kepler’s 2rd law says the planet has to sweep out equal areas in equal times, so the speed of the planet
cannot change.
b. Planets stay at a constant distance from their stars, they don’t move closer or farther away
c. Kepler’s 3rd law says the planet must move fastest when it’s closest, not when it’s farther away.
Answer: C
Chapter 3
1) An unbalanced force must be acting when:
A. An object accelerates
B. An object changes direction, but not speed
C. An object changes speed, but not direction
D. An object changes speed and direction
E. All of the above
Answer: E
2) Your weight equals the force between you and Earth.
Suppose you weigh 60 kg. Then the force on Earth is:
A. 60 kg.
B. Much smaller than 60 kg because your mass is much less than Earth’s.
C. Exactly zero, since only massive objects have gravity.
Answer: A
Explanation: Forces come in pairs of equal size. These act on both bodies.
3) Imagine you are standing at the top of a tall tower. You drop 3 objects shaped like a ball made out of
different materials. Neglecting air resistance, in what order do they hit the ground?
a. Styrofoam, pumpkin, lead
b. Lead, pumpkin, styrofoam
c. Pumpkin, lead, styrofoam
d. All hit at same time
Ans: D
Exp: All have same acceleration
4) Suppose you are transported to a planet with twice the mass of Earth, but the same radius. Your
weight would?
a. Increase
b. Decrease
c. Stay the same
Answer: A
Exp: Radius (distance) is decreasing, so force increases
5) Earth and the Moon have a gravitational force between them. The mass of the Moon is 1.2% of that
of the Earth.
Which statement is incorrect?
A. The force on the Moon is much larger than that on Earth.
B. The forces are equal size, even though the masses are different.
C. The Moon has a larger acceleration than Earth.
Answer: A
Explanation: Statement A is the only incorrect statement. Forces come in pairs of equal size (but
opposite direction). Therefore statement B is correct. Statement C is also correct. The forces are equal,
but the Earth’s mass is much larger. Therefore it will experience a much smaller acceleration than does
the Moon.