1.
What is the shape of an elliptic orbit?
Correct Answer
A. Ellipse
Explanation
An elliptic orbit is shaped like an ellipse, a result of the gravitational forces acting between a central body and the orbiting object. The orbital path, while closed like a circle, is elongated, allowing the orbiting body to come closer to and then farther from the central object in its periodic journey. This elliptical nature is fundamental to understanding how planets and satellites move in their respective orbits, providing a dynamic example of how gravitational forces can shape movement in space.
2.
Which celestial body in our solar system has a nearly perfect elliptical orbit (nearly circular)?
Correct Answer
B. Venus
Explanation
Venus is notable for having the most circular orbit of all the planets in our solar system, which technically still classifies as elliptical with a very low eccentricity. This minimal eccentricity means Venus's orbit deviates very little from a perfect circle, distinguishing it as the planet whose path is closest to circular, thus nearly perfect in terms of being elliptical (circular).
3.
What defines the eccentricity of an elliptic orbit?
Correct Answer
B. Orbit's flatness
Explanation
The eccentricity of an elliptical orbit quantifies how much the path deviates from a perfect circle. In practical terms, eccentricity defines the "flatness" or elongation of the orbit. A higher eccentricity value indicates a more stretched orbit, resembling an elongated oval, while a lower value signifies an orbit closer to a circle, crucial for predicting the orbital mechanics and behavior of celestial bodies.
4.
At which point in its orbit is a planet traveling fastest?
Correct Answer
C. Periapsis
Explanation
According to Kepler's second law, a planet or any object in an elliptic orbit will travel fastest when it is closest to the object it orbits, known as the periapsis. This is because the gravitational pull is strongest at this closest approach, increasing the object's velocity due to the conservation of angular momentum. This principle explains why orbital speed is not constant but varies depending on the object's position along its elliptical path.
5.
What does Kepler's First Law state about elliptic orbits?
Correct Answer
C. Planets orbit in ellipses with the sun at a focus
Explanation
Kepler's First Law, the Law of Ellipses, states that all planets move in elliptical orbits with the Sun at one of the foci, not the geometric center. This positioning of the Sun at a focus, rather than at the center, introduces asymmetry in orbital dynamics, where the distance between a planet and the Sun varies throughout the orbit, influencing seasonal and temperature variations on planets.
6.
Which factor affects the period of an elliptic orbit?
Correct Answer
A. Orbit size and shape
Explanation
The orbital period, or the time it takes for a celestial body to complete one full orbit, is affected by the orbit's size, measured by the semi-major axis, and its shape, determined by the eccentricity. The larger and more elongated the orbit, the longer the orbital period. This relationship is crucial for understanding the timing of celestial events and the behavior of bodies in different orbital paths.
7.
What happens to the orbital speed as a planet approaches apoapsis?
Correct Answer
B. Decreases
Explanation
As a planet moves towards its apoapsis, the point furthest from the central body, its orbital speed decreases. This slowdown occurs due to the decreased gravitational pull at greater distances, which reduces the object's kinetic energy as it climbs further from the gravity well of the central body, reaching a slower speed at the apoapsis before accelerating back as it returns.
8.
What is the significance of the semi-major axis in an elliptic orbit?
Correct Answer
A. Determines the orbit's size
Explanation
The semi-major axis in an elliptical orbit is a critical parameter as it defines the largest diameter of the ellipse and effectively the size of the orbit itself. This measurement is vital for calculating the total area of the orbit and, by Kepler's Third Law, directly influences the orbital period, providing a quantitative measure of how long it takes for an object to complete one revolution around its central body.
9.
What role does the mass of the central body play in an elliptic orbit?
Correct Answer
C. Determines orbital period
Explanation
The mass of the central body in an elliptical orbit plays a critical role in determining the gravitational pull exerted on the orbiting body, thereby affecting its orbital period. According to Kepler's Third Law, the orbital period squared is proportional to the cube of the semi-major axis, moderated by the mass of the central body. Hence, a more massive central body results in a stronger gravitational pull, affecting how quickly an orbiting body moves through its orbit.
10.
How does the gravitational force vary throughout an elliptic orbit?
Correct Answer
D. Varies, strongest at periapsis
Explanation
The gravitational force in an elliptical orbit is not constant but varies according to the distance between the orbiting body and the central body. This force is strongest at the periapsis due to the minimum distance between the two, providing the maximum gravitational pull, and weakest at the apoapsis, where the increased distance reduces the gravitational influence. This variability in gravitational force throughout the orbit is fundamental to the changing speeds and positions of the orbiting body, as it adheres to the laws of celestial mechanics.