Physics 130 Astronomy Exam #1 July 19, 2004

Transcription

1 Physics 130 Astronomy Exam #1 July 19, 2004 Name Multiple Choice: 1. A scientist observes a new phenomenon that disagrees with his explanation or hypothesis. Following the scientific methods, he should a. discard the observation as erroneous. b. modify his hypothesis c. rejects those observations which do not agree with the theory d. wait until someone develops an adequate explanation before announcing his observation. 2. Which fundamental belief about the universe, established by the Greeks and adopted by the early Christian Church, was shattered by Galileo s observation of moons orbiting Jupiter? a. The belief that the Moon was the only moon orbiting around a planet in our solar system. b. The belief that everything in the universe orbits the Earth. c. The belief that everything in the universe orbits the Sun. d. The belief that everything in the visible universe must orbit the center of the Milky Way. 3. An Astronomical Unit (AU) is a. a unit of length, the average distances between the Sun and the Earth. b. a standard unit of length, defined as the wavelength of light from Krypton gas. c. a unit of time, equal to the time taken for the Earth to orbit the Sun once. d. a unit of mass, equal to one solar mass. 4. A light-year is a measure of a. arc length along an orbit b. time c. distance d. the expansion rate of the universe 1

2 5. An astronomer finds an object at a distance of 6.8 AU from the Earth. Which type of object is this likely to be? a. A comet in our solar system b. A distant galaxy c. A star in our Galaxy d. An artificial satellite orbiting the Earth. 6. How much of the overall sky is above the celestial equator, that is, in the northern hemisphere? a. More than one half, because of the precession of the poles b. Exactly one half c. All of it, by definition d. Less than one half, because of the tilt of the equator to the ecliptic plane 7. The zenith defines a direction a. toward the Sun at noon. b. vertically above a point on the equator. c. Vertically above the observer. d. Vertically above the North Pole. 8. The difference in declination angles between the North and South celestial poles is a. variable depending on the season b. 180 c d The nightly motion of objects across our sky is caused by a. the revolution of Earth around the Sun b. the rotation of the Earth on its axis c. the motion of the solar system around the galaxy d. the rotation of the whole celestial sphere of stars around the fixed earth 10. The Sun rises due East in the sky when viewed a. from any site upon Earth on the first day of summer and the first day of winter. b. from any site along the Earth s equator at midsummer and midwinter. c. from any site upon Earth ONLY on the first day of spring and the first day of fall. d. from any site on the equator on everyday of the year. 2

3 11. Over the period of one complete year, an observer at the South Pole would be able to see what fraction of the overall sky? a. 100% b. a variable amount, depending on his longitude c. a variable amount, depending upon which year d. 50% 12. If observed carefully night by night, a particular star will be seen to a. rise about 4 minutes earlier every night b. rise about 4 minutes later every night c. rise at a varying time every night, sometimes earlier, sometimes later than a specified time, because of the Earth s differing orbital speed d. rise at the same time every night 13. A time zone on the Earth, defined for convenience as that region over which civil time is the same at al locations, extends over what range of longitude, on average? a. 1 b. 15 c. 90 d Leap years, containing an extra day, are necessary because a. the Earth s speed of revolution around its orbit varies throughout the year b. the rotation rate of Earth around its axis varies, leading to days of different length c. the length of a year is not an exact number of days d. 365 days is not exactly divisible by The Sun s apparent path across our sky against the background stars (which would be seen if the sunlit sky were not light) is known as a. the great circle b. the ecliptic c. the celestial equator d. the celestial meridian 3

4 16. The Earth would not have seasons if a. its axis of rotation was perpendicular to its equatorial plane. b. the observer s vertical axis were perpendicular to the Earth s orbital plane c. its axis of rotation were perpendicular to its orbital plane d. its equatorial plane were perpendicular to its orbital plane 17. When the Sun is at one of its equinoxes a. the day is longer than the night in one hemisphere of the Earth and shorter in the other hemisphere. b. day and night are of equal length only for people on the equator c. people on the equator have perpetual daylight d. day and night are of equal length everywhere on the Earth 18. Precession is a. the slow coming motion of the spin of the Earth, similar to that of a spinning top b. another name for a parade. c. the motion of the Earth along its orbital path during the year. d. the daily spinning motion of the Earth, producing the apparent motion of the Sun and the stars. 19. At approximately what time will the new moon rise? a. Midnight b. Sunset c. Midday d. Close to sunrise 20. How much of the total surface of the Moon is illuminated by the Sun when it is at quarter phase? a. One quarter b. All of it c. One half d. Very little 4

5 21. A full moon will always be at its highest in our sky at about a. midday b. sunrise c. sunset d. midnight 22. How does the Moon rotate in order to keep one face pointed toward the Earth at all times, a. It does not rotate at all b. It rotates once per day c. It rotates once per year d. It rotates once per month 23. The Moon s path across our sky a. is confined to a band of sky around the ecliptic, the zodiac b. is always along the ecliptic plane, by definition c. can be anywhere in our sky d. is confined to regions north of the celestial equator. 24. What is the phase of the Moon during a total solar eclipse? a. Crescent b. First Quarter c. New d. Full 25. If the plane of the Moon s orbit were to be the same as the ecliptic plane, there would be a lunar eclipse a. once every month b. every day c. twice per month d. only twice per year 26. The Moon does not look completely dark when it is in the Earth s shadow during a total lunar eclipse because a. atmospheric refraction bends red solar light onto the Moon b. there is a remnant glow from the hot lunar surface c. there are faint emissions from the tenuous lunar atmosphere, excited by solar wind bombardment d. of light reflected from the clouds on the Earth, the earthshine 5

6 27. A person standing in the Moon s penumbra will see a. a total lunar eclipse b. a partial lunar eclipse c. a partial solar eclipse d. a total solar eclipse 28. The motions of the planets against the background stars in our sky can best be described as a. general eastward motions but with occasional stationary periods, with no motions at all. b. regular and uniform eastward motion c. regular patterns with general eastward motion interrupted by periods of westward motion. d. Regular patterns with general westward motion interrupted by periods of eastward motion. 29. In the geocentric model for the solar system developed by Ptolemy, to what does the word epicycle refer? a. The length of time from when the planet is furthest from Earth to the next time it is furthest from Earth. b. The large circle (orbit) which carries the planet around the Earth, while the planet itself is moving in a smaller circle. c. A small circle about which a planet moves while the center of this circle moves around the Earth. d. One complete cycle of planetary motions after which the motions repeat themselves (almost) exactly. 30. The Copernican System for planetary motions is a. Earth-centered, with the planets, sun, and stars mounted on crystal spheres, pivoted to allow the correct motions around the Earth. b. Earth-centered, with the planets moving in epicycles around the Earth. c. Sun-centered, with the planets moving in elliptical orbits, the sun being at one focus of the ellipse. d. Sun centered, with the planets moving in perfect circles around the sun. 6

7 31. The phenomenon of parallax is a. the change in apparent position of a nearby object as the observer moves, compared to background objects. b. The apparent change in angular size of an object as it moves toward or away from an observer. c. The change in direction of motion of a planet from retrograde to direct motion. d. The change in the apparent position of an object compared to background objects, as a result of the motion of the object. 32. Tycho Brahe a. developed the first detailed heliocentric model for the solar system, which replaced the geocentric model of Ptolemy. b. Improved the refracting telescope, which allowed him to extend Galileo s observations of the sky. c. Made accurate measurements of planetary motions, which Kepler later used to find the shapes of planetary orbits. d. Developed a reflecting telescope, which used a curved mirror to focus the light. 33. The major contribution of Johannes Kepler to the development of modern astronomy was to a. prove that planetary orbits are ellipses b. develop the first mathematical heliocentric model of the solar system c. use parallax to prove the Earth moves around the Sun. d. observe the satellites (moons) of Jupiter. 34. If an object has an orbit around the sun that has an eccentricity of 0.1, then the orbit is a. a straight line b. exactly circular c. almost circular, but not quite d. a long, thin ellipse 35. Where is a planet when it is moving most rapidly in its orbit? a. At aphelion b. At the focus of its orbit c. At perihelion d. approaching the closest distance to the sun 7

8 36. Kepler s third law, the harmonic law, provides a relationship between a planet s a. Orbital period and mass b. Orbital speed and orbital eccentricity c. Orbital eccentricity and length of semimajor axis d. Orbital period and length of semimajor axis 37. If a planet were to exist in our solar system in a circular orbit with a radius of 3 AU, about how long would it take to orbit the sun once? a. 5.2 years b. 27 years c. 3 years d. 2.1 years 38. What did Galileo see when he observed Venus through his telescope? a. Four satellites (moons) orbiting Venus b. Nothing interesting, since Venus is perpetually cloud covered c. A set of rings d. Phases like the Moon. 39. According to Newton s first law, a. as the rate of change of speed of an object is larger, the larger the force acting upon the object. b. an applied force always causes a change in the direction of travel of an object. c. if no force is acting upon an object then the object s speed and direction of travel will both be constant. d. an applied force always causes a change in the speed of an object. 40. Which path would a planet (like Earth) take if the force of gravity from the Sun were to be suddenly removed? a. The planet would begin to move in a long ellipse with the Sun at one focus. b. The planet would move in a straight-line outward, directly away from the Sun s position. c. The planet would move in a straight line tangential to its present orbit. d. The planet would stop moving altogether since there would now be no gravity acting upon it. 8

9 41. To specify an object s velocity completely, we need to specify a. its direction of travel b. its speed c. the rate of change of its acceleration d. its speed and direction of travel 42. An unbalanced force acting on an object will ALWAYS cause it to a. change its speed or its direction of travel or both b. change its speed c. change its direction of travel d. change its acceleration 43. According to Newton s third law, if a force is acting on an object then a. the object must move in a circular path b. there must be some other force also acting on the object, with the same magnitude but in the opposite direction c. the object must accelerate d. there must be some other force acting on a different object, with the same magnitude but in the opposite direction. 44. The strength of gravity on Mars in about 40% of that on the Earth. If you were to take a standard red brick to Mars, which property of the brick would be significantly different on Mars than on the Earth? a. Its weight b. Its volume c. Its color d. Its mass 45. Suppose that a planet of the same mass as the Earth were orbiting the Sun at a distance of 10 AU. The gravitational force on this planet due to the Sun would be a. 100 times that which the Sun exerts on the Earth b. 1/100 of that which the Sun exerts on the Earth c. 10 times that which the Sun exerts on the Earth d. 1/10 of that which the Sun exerts on the Earth 9

10 46. A person orbiting the Earth in the space station feels weightless because a. two forces are acting on her in opposite directions, so they cancel and produce the same effect as if no force at all were acting. b. only one force (gravity) acts on her, but gravity also accelerates the station so the station does not push up on her to create the feeling of weight. c. her mass is zero in space, and weight requires mass. d. no forces act on her. 47. Which objects are often found to follow parabolic orbits? a. Comets b. No objects all orbits have to be ellipses c. Asteroids d. Small satellites of the outer planets. 48. An object orbiting the sun in a circle can be said to be a. always accelerating b. moving under the action of equal and opposite forces c. moving at a constant velocity d. weightless 49. The purpose of describing planetary orbits in terms of epicycles and deferents was to account for a. the pattern of alternating direct and retrograde motion. b. the general motion of all objects toward the west in the sky each day. c. the fact that a planet s speed in its orbit is fastest when it is closest to the sun. d. the pattern of alternating conjunctions and oppositions. 50. The time period between two successive passages of a planet past a particular star as seen from the sun is a. its sidereal period b. its precessional period c. its synodic period d. its rotational period 10

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