HW3 Fall09 - PHY 317K HOMEWORK # 3 DUE on October 14, 2009...

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PHY 317K HOMEWORK # 3 DUE on October 14, 2009 by 8:00pm Instructions: Use a UT ANSWER SHEET to mark answers. Provide your NAME (last, first), UTEID , and UNIQUE NUMBER of the course. Sign and date it. The answer sheets must be placed in the 317K box located outside PAI 2.48. Late homework will not be graded . Answer the following 76 questions: 1. The approximate value of g at an altitude above Earth equal to one Earth diameter is: A) 9.8 m/s 2 B) 4.9 m/s 2 C) 2.5 m/s 2 D) 1.9 m/s 2 E) 1.1 m/s 2 2. Four particles, each with mass m, are arranged symmetrically about the origin on the x axis. A fifth particle, with mass M , is on the y axis. The direction of the gravitational force on M is: A) B) C) D) E) none of these directions 3. Three particles, two with mass m and one mass M , might be arranged in any of the four configurations known below. Rank the configurations according to the magnitude of the net gravitational force on M , least to greatest. A) 1, 2, 3, 4 B) 2, 1, 3, 4 C) 2, 1, 4, 3 D) 2, 3, 4, 1 E) 1, 3, 2, 4 Page 1
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4. Venus has a mass of about 0.0558 times the mass of Earth and a diameter of about 0.381 times the diameter of Earth. The acceleration of a body falling near the surface of Venus is about: A) 0.21 m/s 2 B) 1.4 m/s 2 C) 2.8 m/s 2 D) 3.8 m/s 2 E) 25 m/s 2 5. To measure the mass of a planet with the same radius as Earth, an astronaut drops an object from rest (relative to the planet) from an altitude of one radius above the surface. When the object hits the surface, its speed is 4 times what it would be if the same experiment were carried out for Earth, ignoring any drag forces from the planets' atmospheres. In units of Earth masses, the mass of the planet is: A) 2 B) 4 C) 8 D) 16 E) 32 6. The mass of a hypothetical planet is 1/100 that of Earth and its radius is 1/4 that of Earth. If a person weighs 600 N on Earth, what would he weigh on this planet? A) 24 N B) 48 N C) 96 N D) 192 N E) 600 N 7. An object is dropped from an altitude of one Earth radius above Earth's surface. If M is the mass of Earth and R is its radius the speed of the object just before it hits Earth is given by: A) / GM R B) /2 GM R C) 2/ GM R D) 2 / GM R E) 2 GM R Page 2
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8. Two particles, each of mass m , are a distance d apart. To bring a third particle, with mass 2 m , from far away to a point midway between the two particles, the work done by an external agent is given by: A) 4 Gm 2 / d B) –4 Gm 2 / d C) 8 Gm 2 / d D) –8 Gm 2 / d E) zero 9. The escape velocity at the surface of Earth is approximately 11 km/s. What is the mass, in units of Earth's mass, of a planet with twice the radius of Earth for which the escape speed is twice that for Earth? A) 2 B) 4 C) 8 D) 1/2 E) 1/4 10. Neglecting air resistance, the escape speed from a certain planet for an empty space vehicle is 1.12 × 10 4 m/s. What is the corresponding escape speed for the fully loaded vehicle which has triple the mass of the empty one?
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This note was uploaded on 12/02/2009 for the course PHY 317k taught by Professor Kopp during the Spring '07 term at University of Texas at Austin.

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HW3 Fall09 - PHY 317K HOMEWORK # 3 DUE on October 14, 2009...

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