Astronomy quiz #2 – Flashcards
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The Ptolemaic model of the universe:
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explained and predicted the motions of the planets with deferents and epicycles.
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Scientists today do not accept the Ptolemaic model because:
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the work of Tycho and Kepler showed the heliocentric model was more accurate.
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When a planet retrogrades, it appears to move westward for weeks at a time.
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True
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On which of these assumptions do Ptolemy and Copernicus agree?
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All orbits must be perfect circles.
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The heliocentric model was actually first proposed by:
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Aristarchus.
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According to Copernicus, the retrograde motion for Mars must occur
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at opposition, when the earth overtakes Mars and passes between Mars and the Sun.
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Which was a contribution to astronomy made by Copernicus?
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He laid out the order and relative motion of the known solar system.
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Which of these was NOT seen telescopically by Galileo?
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stellar parallax
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Which of these was NOT a telescopic discovery of Galileo?
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the moons of Saturn
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A fatal flaw with Ptolemy's model is its inability to predict the observed phases of
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Mercury and Venus.
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Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as
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elliptical, not circular
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Tycho Brahe's contribution to Kepler's Laws of Planetary Motion were
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his detailed and accurate observations of the planet's position.
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A circular orbit would have an eccentricity of
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0.
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Upon which point do Copernicus and Kepler disagree?
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The orbits of the planets are ellipses, with one focus at the Sun.
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Which concept was NOT a part of Kepler's Laws of Planetary Motion?
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Epicycles are needed to explain the varying brightnesses of the planets.
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What does Kepler's third law imply about planetary motion?
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Planets further from the Sun orbit at a slower speed than planets closer to the Sun.
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A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years?
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sq 27
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The Law of Universal Gravitation was developed by:
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Newton.
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The force of gravity between two objects:
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increases with the masses of the bodies, but decreases with the square of the distances between them.
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According to Newton's Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would
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decrease by a factor of 9.
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If the distance between two asteroids is doubled, the gravitational force they exert on each other will
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be one fourth as great
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Orbital speed is the speed with which a planet moves around the Sun. This speed is determined by
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the mass of both the planet and the Sun and the distance between the two.
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Escape velocity is the speed required to
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overcome the graviational pull of an object.
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According to Copernicus, retrograde motion for Venus must occur around
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inferior conjunction, when it passes between us and the Sun.
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Kepler's second law implies what about planetary motion?
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A planet moves faster when it is closer to the Sun.
