Phys133 SAMPLE Questions for Midterm#1

Phys133 SAMPLE questions for MidTerm#1

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MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1) Which of the following is largest? 1) A) 1 light-year B) size of Pluto's orbit C) size of a typical galaxy D) distance to the nearest star (other than our Sun)

2) What is an astronomical unit? 2) A) the average speed of the earth around the Sun B) any basic unit used in astronomy C) the length of time it takes the earth to revolve around the Sun D) the average distance from the earth to the Sun E) the diameter of the earth's orbit around the Sun

3) Roughly how many stars are in the Milky Way Galaxy? 3) A) 100 million B) 100 trillion C) 1 billion D) 100 billion E) 10 billion

4) Suppose you live on the Moon. How long is a day (i.e., from sunrise to sunrise)? 4) A) a year B) 23 hours 56 minutes C) 24 hours D) about 18 years E) a lunar month

5) What is a circumpolar star? 5) A) a star that is visible from the Arctic or Antarctic circles B) a star that is close to the south celestial pole C) a star that always remains above your horizon D) a star that makes a daily circle around the celestial sphere E) a star that is close to the north celestial pole

6) How can an electron in an atom lose energy to go from a higher energy level to a lower energy 6) level? A) It loses gravitational potential energy. B) It absorbs a photon equal in energy to its own energy drop. C) It exchanges gravitational potential energy for kinetic energy. D) It releases a photon equal in energy to its own energy drop. E) It loses kinetic energy.

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7) When someone on the earth observes the Moon in the ﬁrst-quarter phase, someone on the Moon 7) facing the earth observes the earth in the A) ﬁrst-quarter Earth phase. B) third-quarter Earth phase. C) full Earth phase. D) crescent Earth phase. E) new Earth phase.

8) What do the structures of Stonehenge, the Templo Mayor, the Sun Dagger, and the Big Horn 8) Medicine Wheel all have in common? A) They all can be used as lunar calendars. B) They were all built on the orders of ancient kings. C) They were all used by ancient peoples for astronomical observations. D) They were all places used for religious sacriﬁce. E) all of the above

9) Astronomers infer that the universe is expanding because distant galaxies all appear to 9) A) be growing in size. B) be made of dark matter. C) be moving away from us, with more distant ones moving faster. D) rotate rapidly.

10) Earth is farthest from the Sun in July and closest to the Sun in January. During which northern 10) hemisphere season is Earth moving fastest in its orbit? A) winter B) summer C) fall D) spring

11) Where is our solar system located within the Milky Way Galaxy? 11) A) very near the center of the galaxy B) It is located in the halo of the galaxy. C) at the far edge of the galaxy's visible disk D) roughly halfway between the center and the edge of the visible disk of the galaxy

12) Which scientists played a major role in overturning the ancient idea of an Earth-centered 12) universe, and about when? A) Newton and Einstein; about 100 years ago B) Aristotle and Copernicus; about 400 years ago C) Aristotle and Plato; about 2,000 years ago D) Copernicus, Kepler, and Galileo; about 400 years ago E) Huygens and Newton; about 300 years ago

13) How many arcseconds are in 1°? 13) A) 3,600 B) 60 C) 10,000 D) 360 E) 100

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14) What makes the North Star, Polaris, special? 14) A) It is the brightest star in the sky. B) It is the star straight overhead. C) It appears very near the north celestial pole. D) It can be used to determine your longitude on Earth. E) It is the star directly on your northern horizon.

15) The great contribution of Nicholas Copernicus was to 15) A) create a detailed model of our solar system with the Sun rather than Earth at the center. B) discover the laws of planetary motion. C) prove that the earth is not the center of the universe. D) discover the law of gravity.

16) An atom which has 4 protons and 6 neutrons will be electrically neutral if it contains 16) A) at least one electron. B) 4 electrons. C) 6 electrons. D) 10 electrons.

17) Which of the following represents a case in which you are not accelerating? 17) A) going from 0 to 60 miles per hour in 10 seconds B) driving in a straight line at 60 miles per hour C) driving 60 miles per hour around a curve D) slamming on the brakes to come to a stop at a stop sign

18) Suppose the Sun were to suddenly shrink in size but its mass remained the same. According to 18) the law of conservation of angular momentum, what would happen? A) The Sun's rate of rotation would slow. B) This could never happen, because it is impossible for an object to shrink in size without an outside torque. C) The Sun would rotate faster than it does now. D) The Sun's angular size in our sky would stay the same.

19) Suppose you see two stars: a blue star and a red star. Which of the following can you conclude 19) about the two stars? Assume that no Doppler shifts are involved. A) The red star is more massive than the blue star. B) The blue star is more massive than the red star. C) The blue star has a hotter surface temperature than the red star. D) The red star has a hotter surface temperature than the blue star. E) The blue star is farther away than the red star.

20) At approximately what time would a full moon be on your meridian? 20) A) midnight B) 6 A.M. C) noon D) 9 A.M. E) 6 P.M.

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21) According to the universal law of gravitation, if you triple the distance between two objects, then 21) the gravitational force between them will A) increase by a factor of 3. B) decrease by a factor of 3. C) decrease by a factor of 9. D) increase by a factor of 9. E) decrease by a factor of 6.

22) If an object's velocity is doubled, its momentum is 22) A) quadrupled. B) dependent on its acceleration. C) unchanged. D) doubled. E) halved.

23) According to the universal law of gravitation, if you double the masses of both attracting objects, 23) then the gravitational force between them will A) not change at all. B) decrease by a factor of 4. C) decrease by a factor of 2. D) increase by a factor of 2. E) increase by a factor of 4.

24) From Kepler's third law, an asteroid with an orbital period of 8 years lies at an average distance 24) from the Sun equal to A) 4 astronomical units. B) 16 astronomical units. C) 2 astronomical units. D) 8 astronomical units. E) It depends on the asteroid's mass.

25) How did Eratosthenes estimate the size of the earth in 240 B.C.? 25) A) by measuring the size of the earth's shadow on the Moon in a lunar eclipse B) by observing the duration of a solar eclipse C) by sending ﬂeets of ships around the earth D) by comparing the maximum altitude of the Sun in two cities at different latitudes E) We don't know how he did it since all his writings were destroyed.

26) An atom of the element iron has an atomic number of 26 and an atomic weight of 56. If it is neutral, 26) how many protons, neutrons, and electrons does it have? A) 13 protons, 43 neutrons, 13 electrons B) 13 protons, 56 neutrons, 13 electrons C) 26 protons, 30 neutrons, 30 electrons D) 26 protons, 56 neutrons, 26 electrons E) 26 protons, 30 neutrons, 26 electrons

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27) Which of the following statements best describes the two principal advantages of telescopes over 27) eyes? A) Telescopes collect more light and are unaffected by twinkling. B) Telescopes have much more magniﬁcation and better angular resolution. C) Telescopes can see farther without image distortion and can record more accurate colors. D) Telescopes can collect far more light with far better angular resolution. E) Telescopes can collect far more light with far greater magniﬁcation.

28) We can see each other in the classroom right now because we 28) A) emit thermal radiation. B) reﬂect visible light. C) reﬂect infrared light. D) emit visible light. E) emit infrared light.

29) The wavelength of a wave is 29) A) the distance between a peak of the wave and the next trough. B) the distance between two adjacent peaks of the wave. C) the distance between where the wave is emitted and where it is absorbed. D) equal to the speed of the wave times the wave's frequency. E) how strong the wave is.

30) What does temperature measure? 30) A) the total potential energy of particles in a substance B) the total number of particles in a substance C) the average kinetic energy of particles in a substance D) the average mass of particles in a substance E) the average size of particles in a substance

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SHORT ANSWER. Answer the questions, showingh your work for any calculations.

31) a. Suppose it takes 6 seconds for a watermelon to fall to the ground after being dropped 31) from the top of a tall building.

a. If there were no air resistance, so that the watermelon falls with the acceleration of gravity, about how fast (in m/s) would it be going when it hit the ground?

b. If the watermelon were dropped from the same height on planet with twice the mass and twice the radius of the earth, what how fast (in m/s) would it hit the ground.

32) Suppose a star four times more massive than our Sun has a planet the same mass as 32) Earth, orbiting at a distance of 1 AU. a. What is the orbital period of the planet?

b. Recalling that the earth's speed around the sun is 30 km/s, what is the orbital speed (in km/s) of this planet?

c. How would the above answer change if the planet had twice the mass of earth?

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33) Suppose the surface temperature of the Sun were about 18,000 K, rather than 6,000 K . 33)

a. How much more thermal radiation would the Sun emit?

b. How would the wavelength of the maximum in it spectrum change? Give an estimated value in nm.

34) A spectral line that has rest wavelength of 600 nm is observed in the spectrum of a star 34) to have a wavelength of 600.3 nm.

a. Is the star moving away or toward the observer?

b. What is the fraction, v/c, the star's speed v to the speed of light c?

c. Given that the speed of light is c=300,000 km/s, what is the star's speed in km/s?

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35) Two stars orbiting around each other with a separation of s=10 AU appear to separated 35) by an angle a=1 arcsec.

a. What is the distance d (in parsec) to the stars?

b. How would the angular separation "a" change if the stars were moved to twice as far away?