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Unformatted text preview: salazar (ggs332) HW01 Tsoi (58160) 1 This printout should have 24 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points A mass attached to a spring oscillates back and forth as indicated in the position vs. time plot below. P x t At point P, the mass has 1. positive velocity and zero acceleration. 2. negative velocity and positive accelera tion. 3. zero velocity and zero acceleration. 4. zero velocity but is accelerating (posi tively or negatively). 5. positive velocity and negative accelera tion. correct 6. positive velocity and positive accelera tion. 7. negative velocity and negative accelera tion. 8. negative velocity and zero acceleration. Explanation: The velocity is positive because the slope of the curve at P is positive. The acceleration is negative because the curve is concave down at P. 002 10.0 points One cubic meter (1.0 m 3 ) of aluminum has a mass of 2700 kg, and a cubic meter of iron has a mass of 7860 kg. Find the radius of a solid aluminum sphere that has the same mass as a solid iron sphere of radius 4 . 44 cm. Correct answer: 6 . 33971 cm. Explanation: Let : m Al = 2700 kg , m Fe = 7860 kg , and r Fe = 4 . 44 cm . Density is = m V . Since the masses are the same, Al V Al = Fe V Fe Al parenleftbigg 4 3 r 3 Al parenrightbigg = Fe parenleftbigg 4 3 r 3 Fe parenrightbigg parenleftbigg r Al r Fe parenrightbigg 3 = Fe Al r Al = r Fe 3 radicalbigg Fe Al = (4 . 44 cm) 3 radicalBigg 7860 kg 2700 kg = 6 . 33971 cm . 003 (part 1 of 2) 10.0 points Consider the positiontime graph for a squir rel running along a clothesline. b b b b b b 1 2 3 4 5 1 2 3 4 1 2 time (s) position(m) What is the squirrels displacement at the time t = 3 . 0 s? Your answer must be within 5.0% Correct answer: 2 m. Explanation: salazar (ggs332) HW01 Tsoi (58160) 2 Let : x f = 2 m and x i = 0 m . The displacement is x = x f x i = ( 2 m) (0 m) = 2 m . 004 (part 2 of 2) 10.0 points What is the squirrels average velocity during the time interval between 0.0 s and 3.0 s? Your answer must be within 5.0% Correct answer: . 666667 m / s. Explanation: Let : t = 3 . 0 s . v avg = x t = 2 m 3 s = . 666667 m / s . 005 10.0 points Consider three position curves between time points t A and t B . s B s A B A t A t B 3 2 1 t s Choose the correct relationship among quantities v 1 , v 2 , and v 3 . v = v A + v B 2 when a is a constant. 1. v 1 &lt; v 2 &lt; v 3 2. v 1 = v 2 = v 3 correct 3. v 1 &gt; v 2 &gt; v 3 Explanation: The average velocity of an object is v = displacement time = s B s A t B t A . All three curves have exactly the same change in position s = s B s A in exactly the same time interval t = t B t A , so all three average velocities are equal: v 1 = v 2 = v 3 ....
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 Spring '10
 TSOI
 Physics, Mass

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