midterm_answers_fall06 - GE 70A MIDTERM ANSWERS Nov 2 2006...

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1 GE 70A MIDTERM ANSWERS Nov 2, 2006. 11:00 AM to 12:15 PM Name ____KEY__________________________________________________________ Student ID number: ______________________________________________________ This is a three-part exam. Use the scantron provided to answer Part I (be sure to put your name on it, and to bubble in your name and student ID number on the back of the scantron form). Write your answers to Parts II and III on these exam pages. Divide your time judiciously between Part I (40%), Part II (15%) and Part III (45%). A calculator may be used for this exam, but the calculations required are simple enough that it is not essential. Part I : Multiple Choice (1 point each, total 40 points). Provide the single best answer to each of the following 40 questions or statements. There is no penalty for guessing, so if you can eliminate an answer or two, then you might as well make an educated guess. If two answers seem possible, choose the one that responds best to what is being asked. 1. Astronomers can tell how far away a distant galaxy is by a. Measuring how long it takes for the light from a star in that galaxy to reach us b. Measuring how much dust is in the way absorbing the light coming from that galaxy c. Measuring the cosmic microwave background d. Finding a standard candle such as a supernova or a variable star in that galaxy and using the inverse square law of light e. Finding the gravitational pull of the galaxy 2. What determines the length of a year? a. the rotation of the Earth on its axis b. the revolution of the Earth about the Sun c. the length of time required for the Moon to circle the Earth 12 times d. the number of oscillations of a cesium atom e. the period of the wobble (precession) of the Earth s rotation axis 3. The earliest stages of planet formation in the solar nebula (or in any protostellar gas cloud) is believed to occur by: a. near-collisions between stars, which pull matter out of the stars that then condenses into planets b. self-gravity of the gas in the nebula c. the gravitational effect of dark matter, causing baryonic matter to sink into the pools of dark matter and form planets there d. magnetic formations (vortices) in the rotating gas disk, which eventually cool and collapse to form planets e. the coalescence of dust particles in the midplane of the nebula, building up to ever larger bodies until they are big enough for gravity to take over
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2 4. If you were an extraterrestrial living on a planet in a galaxy 5 billion light years away from the Milky Way galaxy, what velocity pattern would you detect for the galaxies around you? a. Most are receding—the ones farther away are receding slower b. Most are receding—the ones farther away are receding faster c. The galaxies around you are not moving relative to you d. Most are coming towards you—the ones farther away are moving faster e. Most are coming towards you—the closer ones are moving faster 5. Nuclear fusion in stars does not produce
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midterm_answers_fall06 - GE 70A MIDTERM ANSWERS Nov 2 2006...

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