1.
Kepler’s third law states that the relationship between the orbital period and semi-major axis of a planet’s orbit is P2 = a3. To use this equation for planets orbiting the Sun, P must be expressed in and a must be expressed in:
Correct Answer
E. (e) years; astronomical units.
2.
Imagine that you throw a ball directly upward. Which of the following statements best describes how Newton’s Second Law accounts for the motion of the ball when it reaches its maximum height?
Correct Answer
C. (c) The ball has a net force that is downward and an acceleration that is downward.
Explanation
When the ball reaches its maximum height, its velocity becomes zero. According to Newton's Second Law, the net force acting on an object is equal to its mass multiplied by its acceleration. Since the ball is moving upward and its velocity is decreasing, there must be a net downward force acting on it. This downward force causes the ball to decelerate and eventually come to a stop at its maximum height. Therefore, option (c) best describes how Newton's Second Law accounts for the motion of the ball when it reaches its maximum height.
3.
Communications satellites are often placed in orbits 36,000 km from the Earth. These satellites are geosynchronous since they remain fixed above the same position on the Earth. These satellites have an orbital period of...
Correct Answer
B. (b) 1 day
Explanation
Communications satellites that are placed in orbits 36,000 km from the Earth are geosynchronous, meaning they remain fixed above the same position on the Earth. Since the Earth takes approximately 24 hours to complete one rotation, these satellites have an orbital period of 1 day. This allows them to maintain a constant position relative to the Earth's surface, making them ideal for communication purposes.
4.
Does your observation of Venus in this phase provide evidence that refutes the Ptolemaic (Ancient Greek) model of the Solar System?
Correct Answer
A. (a) Yes
Explanation
Observing Venus in this phase provides evidence that refutes the Ptolemaic model of the Solar System because according to the Ptolemaic model, Venus should always be seen close to the Sun and never in a crescent phase. However, the observation of Venus in this phase contradicts the Ptolemaic model, suggesting that Venus can indeed be seen in a crescent phase and therefore supporting the heliocentric model of the Solar System.
5.
You observe two stars over the course of a year (or more) and find that: Star A has a parallax angle of 1 arcsecond Star B has a parallax angle of 1/2 arcseconds How do the distances to the stars compare?
Correct Answer
B. (b) Star B is further away than star A.
Explanation
The parallax angle is inversely proportional to the distance to the star. Since Star A has a larger parallax angle than Star B, it means that Star A is closer to us than Star B. Therefore, Star B is further away than Star A.
6.
The concept of the epicycle was used to explain:
Correct Answer
A. (a) retrograde motion of the planets using the geocentric theory.
Explanation
The concept of the epicycle was used to explain the retrograde motion of the planets using the geocentric theory. In the geocentric model, it was believed that the Earth was at the center of the universe and the planets moved in perfect circles around it. However, the observed retrograde motion, where planets appeared to move backward in the sky, was inconsistent with this model. To account for this, the concept of the epicycle was introduced, which proposed that planets moved in small circles called epicycles, while also moving along their larger orbit around the Earth. This explanation helped to reconcile the observed retrograde motion with the geocentric theory.
7.
Which of the following best describes the normal (prograde) motion of the planets?
Correct Answer
D. (d) Planets rise in the east and set in the west. Over the course of several months, they appear to drift from west to east with respect to the distant stars.
Explanation
The correct answer is (d) Planets rise in the east and set in the west. Over the course of several months, they appear to drift from west to east with respect to the distant stars. This is because the planets orbit the Sun in the same direction as the Earth, causing them to move from east to west across the sky. However, due to the Earth's own rotation, they appear to rise in the east and set in the west. Over time, as the Earth moves in its orbit, the planets appear to drift from west to east with respect to the distant stars.
8.
Mars rises tonight at the exact same time as a particular star. If Mars is in retrograde motion, then tomorrow night Mars will:
Correct Answer
A. (a) rise earlier than this star.
Explanation
When a planet is in retrograde motion, it appears to be moving backwards in the sky relative to the stars. Since Mars rises at the same time as a particular star tonight, if Mars is in retrograde motion, it means that it is moving slower than the star. Therefore, tomorrow night Mars will rise earlier than this star, as it continues to move backwards in its orbit.
9.
If a small weather satellite and the large International Space Station are orbiting Earth at the same altitude above Earths surface, which object takes longer to orbit once around Earth?
Correct Answer
C. (c) They would take the same amount of time
Explanation
The small weather satellite and the large International Space Station are both orbiting at the same altitude above Earth's surface. Since the altitude is the same, the gravitational pull on both objects is also the same. Therefore, both objects would experience the same gravitational force and would have the same orbital period. Hence, they would take the same amount of time to orbit once around Earth.
10.
Compared to its angular momentum when it is farthest from the Sun, Pluto’s angular momentum when it is nearest to the Sun is
Correct Answer
C. (c) the same
Explanation
When an object is closer to the Sun, its angular momentum remains the same. Angular momentum is the product of an object's mass, velocity, and the radius of its orbit. In this case, since the mass and velocity of Pluto remain constant, the only variable that changes is the radius of its orbit. As Pluto moves closer to the Sun, the radius of its orbit decreases, but this decrease is compensated by an increase in its velocity. Therefore, the angular momentum of Pluto remains the same when it is nearest to the Sun as when it is farthest from the Sun.
11.
Which of the following represents a case in which you are not accelerating?
Correct Answer
A. (a) Driving in a straight line at 60 miles per hour
Explanation
In a straight line at a constant speed of 60 miles per hour, there is no change in velocity. Since acceleration is the rate of change of velocity, if the velocity remains constant, there is no acceleration. Therefore, driving in a straight line at 60 miles per hour represents a case in which you are not accelerating.
12.
Which of the following best compares your mass and weight if you are standing on the Earth versus standing on Mars?
Correct Answer
C. (c) Your weight will be greater on Earth and your mass will be the same.
Explanation
When comparing mass and weight, it is important to understand the difference between the two. Mass refers to the amount of matter in an object, while weight is the force of gravity acting on that object. The question asks about the comparison between standing on Earth and standing on Mars. Since weight is determined by gravity, and the gravity on Earth is stronger than on Mars, your weight would be greater on Earth. However, mass remains the same regardless of location, so your mass would be the same on both Earth and Mars. Therefore, the correct answer is (c) Your weight will be greater on Earth and your mass will be the same.
13.
Kepler’s third law states that a planet’s orbital period, P, is related to its semi-major axis, a, according to the mathematical relationship P2 = a3. Which of the following statements describe a characteristic of the solar system that is explained by Kepler’s third law?
Correct Answer
A.
(a) Inner planets orbit the Sun at higher speed than outer planets.
Explanation
Kepler's third law states that a planet's orbital period is related to its semi-major axis. This means that planets that are closer to the Sun will have a shorter orbital period than planets that are farther away. Therefore, the inner planets, which are closer to the Sun, will orbit the Sun at a higher speed than the outer planets.
14.
The table below shows the orbital distances, orbital periods, and masses for the six planets closest to the Sun. Jupiter is the most massive of these planets at 318 times the mass of the Earth and Mercury is the least massive of these planets at 0.06 times the mass of the Earth.
The asteroid Atira has an orbital period of P = 0.64 years. Using the data from the table in the previous question, the Asteroid Atira has a semi-major axis of:
Correct Answer
C. (c) 0.74 A.U.
Explanation
The semi-major axis of an orbit can be calculated using Kepler's third law, which states that the square of the orbital period is proportional to the cube of the semi-major axis. Since the orbital period of the asteroid Atira is given as 0.64 years, we can use this information to find the semi-major axis. Taking the cube root of 0.64, we get approximately 0.74. Therefore, the semi-major axis of the asteroid Atira is 0.74 astronomical units (A.U.).
15.
Which of the following lettered locations corresponds to the phase of Venus shown below (as viewed from the location of the Earth marked on the diagram)?
Correct Answer
B. B
Explanation
The correct answer is B because it is the only location that corresponds to the phase of Venus shown in the diagram. The diagram indicates that Venus is in a crescent phase, with only a small portion of the planet illuminated. Location B is the only one that matches this description, as it is positioned in a way that would allow the Earth to view Venus in this specific phase.
16.
In each figure below three rocky asteroids are shown with masses (m), expressed in arbitrary units, separated by a distance (d), also expressed in arbitrary units. The asteroids are identified with the letters A, B, and C.
Which asteroid exerts a stronger gravitational force on the asteroid labeled C?
Correct Answer
A. (a) Asteroid A
Explanation
Asteroid A exerts a stronger gravitational force on asteroid C because it is closer to asteroid C compared to asteroid B. According to the law of universal gravitation, the force of gravity between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Since the masses of the asteroids are not given, we can assume that they are equal. Therefore, the closer the objects are, the stronger the gravitational force between them.
17.
Use the drawing below to answer the next three questions. In this picture the Earth-Moon system is shown (not to scale) along with three possible positions A–C for a spacecraft traveling from the Earth to the Moon. Note that position B is exactly half way between the Earth and the Moon.
When the spacecraft is at the half-way point between the Earth and the Moon (point B) which object exerts the largest gravitational force on the spacecraft?
Correct Answer
B. (b) The Earth.
Explanation
When the spacecraft is at the half-way point between the Earth and the Moon (point B), the Earth exerts the largest gravitational force on the spacecraft. This is because the gravitational force between two objects depends on their masses and the distance between them. Although the Moon is closer to the spacecraft at point B, the Earth's mass is much larger than the Moon's, resulting in a stronger gravitational force exerted by the Earth. Therefore, the Earth exerts the largest gravitational force on the spacecraft at this point.
18.
Use the drawing below to answer the next three questions. In this picture the Earth-Moon system is shown (not to scale) along with three possible positions A–C for a spacecraft traveling from the Earth to the Moon. Note that position B is exactly half way between the Earth and the Moon.
At which location (A, B or C) would the spacecraft be when the gravitational force exerted by the Earth on the spacecraft is the weakest?
Correct Answer
C. C
Explanation
The gravitational force exerted by a celestial body decreases with distance. Since position C is the farthest from the Earth compared to positions A and B, the gravitational force exerted by the Earth on the spacecraft would be the weakest at location C.
19.
During which part of the planets orbit (A, B or C) is the planet moving slowest. Answer D if you think that the planet is traveling at the same speed through all the portions of the motion (A, B and C).
Correct Answer
C. C
Explanation
The planet is moving slowest during part C of its orbit.
20.
A star is 50 parsecs away. What maximum separation between the end points of the star’s apparent motion over the course of a year?
Correct Answer
B. (a) 1/25 arcseconds
Explanation
The planet is moving slowest during part C of its orbit.
21.
During how many portions of the planets orbit (A, B or C) would the planet experience an increase in speed for at least one moment.
Correct Answer
C. (c) During all three portions shown.
Explanation
The question asks about the portions of the planet's orbit where it experiences an increase in speed. From the given answer choices, option (c) states that the planet experiences an increase in speed during all three portions shown. This means that at some point in each portion, the planet's speed increases. Therefore, option (c) is the correct answer.
22.
Which of the orbits below obeys Kepler’s 1st law of planetary motion?
Correct Answer
A. A