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Unformatted text preview: salazar (ggs332) HW01 Tsoi (58160) 1 This print-out should have 24 questions. Multiple-choice 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 position-time 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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