Homework 2 ASTR

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University of Illinois, Urbana Champaign *

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100

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Astronomy

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Apr 3, 2024

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pdf

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1/30/24, 10:16 PM Homework 2: Attempt review | Learn@Illinois 1/30/24, 10:16 PM Homework 2: Attempt review | Learn@Illinois Question 3 Correct 1.00 points out of 1.00 Started on Wednesday, January 24, 2024, 9:07 PM State Finished What path would a planet (like the Earth!) take if the force of gravity from the Sun were to be suddenly removed? Completed on Wednesday, January 24, 2024, 9:45 PM Select one: Time taken 38 mins 16 secs Points 40.00/40.00 A. The planet would move in a straight line outward, directly away from the Sun's position. Grade 25.00 out of 25.00 (100%) B. The planet would move in a straight line tangential to its present orbit. # Correct! Feedback Excellent work! C. The planet would stop moving altogether because there would be no gravity acting on it. D. The planet would begin to move in a long ellipse with the Sun at one focus. Question 1 Correct 1.00 points out of 1.00 Question 4 Correct . . . 1.00 points out of 1.00 The purpose of describing planetary orbits in terms of epicycles and deferents was to account for Select one: The Copernican system for planetary motions is A. the observed pattern of phases, like the Moon's. B. the fact that a planet's speed in its orbit is fastest when it is closest to the Sun. Select one: C. the general motion of all objects toward the west in the sky each day. A. Earth-centered, with the planets, the Sun, and the stars mounted on crystal spheres, pivoted to allow the correct motions around the D. the pattern of alternating prograde and retrograde motion. «# Correct! Earth. Sun-centered, with the planets moving in elliptical orbits, the Sun being at one focus of the ellipse. C. Sun-centered, with the planets moving in perfect circles around the Sun. «# Correct! Question 2 D. Earth-centered, with the planets moving in epicycles around the Earth. Correct 1.00 points out of 1.00 Question 5 Correct The word "planet” is derived from a Greek term meaning 1,00 points out of 1.00 Select one: A. non-twinkling star. Which of the following lists of different types of electromagnetic radiation is correctly ordered in wavelength, from shortest to longest? B. astrological sign. C. bright nighttime object. Select one: D. wanderer.« Correct! A. Gamma rays, ultraviolet, infrared, radio « Correct! Gamma rays, ultraviolet, radio, infrared C. Radio, ultraviolet, infrared, gamma rays Radio, infrared, ultraviolet, gamma rays https://learn.illinois.edu/mod/quiz/review.php?attempt=32235711&cmid=8198810 114 https://learn.illinois.edu/mod/quiz/review.php?attempt=32235711&cmid=8198810 2/14

1/30/24, 10:16 PM Homework 2: Attempt review | Learn@Illinois Question 6 Correct 1.00 points out of 1.00 Halley's Comet returns to the Sun's vicinity approximately every 76 years in an elliptical orbit. According to Kepler's third law, what will be the semi-major axis of this orbit? Select one: A. 179AU« Correct! B. 1AU C. 0.59AU D. 50.000 AU Question 7 Correct 1.00 points out of 1.00 Consider a comet in a long, thin elliptical orbit with a semi-major axis of 1 AU. What can you say about the orbital period of this comet? Select one: A. It will be more than one year. It will be less than one year. B C. It will be oneyear. ¥ Correct! D It is not possible to determine the comet's sidereal period without knowing the eccentricity of its orbit. Question 8 Correct 1.00 points out of 1.00 X-rays and visible light Select one: A. are the same thing except that X-rays have longer wavelengths than visible light. B. are different because X-rays are made up of waves, whereas light is made up of particles. C. are different because X-rays are made up of particles, whereas light is made up of waves. D are the same thing except that X-rays have shorter wavelengths than visible light. ¥ Correct! https://learn.illinois.edu/mod/quiz/review.php?attempt=32235711&cmid=8198810 1/30/24, 10:16 PM Homework 2: Attempt review | Learn@Illinois Question 9 Correct 1.00 points out of 1.00 A particular photon has a wavelength of 450 nm and a second one has a wavelength of 580 nm. Which of the following statements is true for the energies of these two photons? Select one: A. All photons have the same energy, regardless of wavelength. B. The 450-nm photon has the higher energy. « Correct! C. The photon from the higher-intensity light source has the higher energy (regardless of wavelength). D. The 580-nm photon has the higher energy. Question 10 Correct 1.00 points out of 1.00 A person orbiting the Earth in the Space Shuttle feels weightless because Select one: A. her mass is zero in space, and weight requires mass. B. no forces act on her. C. two equal forces are acting on her in opposite directions - the forces therefore cancel each other out. D only one force (gravity) acts on her, but gravity also accelerates the Shuttle, so the Shuttle does not push up on herto « Correct! create the feeling of weight. Question 11 Correct 1.00 points out of 1.00 Which of the following would cause the Earth’s gravitational force on the Moon to increase by the largest amount? Select one: A. Double the mass of Earth. B. Due to Newton's third law, the Moon's force on Earth will always be the same size as the Earth's force on the Moon so none of the changes listed in the other choices could cause the force to increase. C. Double the mass of the Moon. Move the moon to half its current distance from the Earth. «# Correct! https://learn.illinois.edu/mod/quiz/review.php?attempt=32235711&cmid=8198810 4/14

1/30/24, 10:16 PM Question 12 Correct 1.00 points out of 1.00 The major reason why astronomers seek funds to build larger telescopes is Select one: A. to measure a wider spectrum of light from stars. B. to collect more light from distant objects. # Correct! C. to provide magnified images of stars. D. to bring stars closer to the Earth. Question 13 Correct 1.00 points out of 1.00 To which point in a planetary orbit does the word “aphelion” refer? Select one: A. The precise center of the orbit B. The “other” focus (the one not occupied by the Sun) C. The point farthest from the Sun « Correct! D. The point closest to the Sun Question 14 Correct 1.00 points out of 1.00 In which order (from earliest to latest) did the following people make their major contributions to astronomy? Select one: A. B C D Copernicus, Kepler, Brahe, Newton Brahe, Copernicus, Newton, Kepler Kepler, Copernicus, Brahe, Newton Copernicus, Brahe, Kepler, Newton + Correct! https://learn.illinois.edu/mod/quiz/review.php?attempt=32235711&cmid=8198810 Homework 2: Attempt review | Learn@Illinois 1/30/24, 10:16 PM Homework 2: Attempt review | Learn@Illinois Question 15 Correct 1.00 points out of 1.00 The direction of retrograde motion for a planet as seen by an observer on the Earth is Select one: A. from west to east relative to the background stars. B. from east to west relative to the background stars. # Correct! C. from west to east relative to objects on the person's horizon. D. from east to west relative to objects on the person's horizon. Question 16 Correct 1.00 points out of 1.00 The asteroid Ceres orbits the Sun at an average distance of 2.8 AU. What is Ceres' orbital period around the Sun? Select one: A. 46.8 years B. 4.68 years ¢« Correct! C. 28years 1.99 years Question 17 Correct 1.00 points out of 1.00 Mars moves in an elliptical orbit around the Sun. The location of the Sun relative to this ellipse is Select one: A B C D at one end of the major axis of the ellipse. at the focus that is closer to the point where Mars is moving the slowest. at the focus that is closer to the point where Mars moves the fastest. ¥ Correct! at the exact center of the ellipse. 514 https://learn.illinois.edu/mod/quiz/review.php?attempt=32235711&cmid=8198810 6/14

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