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Unformatted text preview: midterm 04 BOBBITT, JAMES Due: May 2 2007, 11:00 pm 1 Version number encoded for clicker entry: V1:1, V2:1, V3:2, V4:3, V5:1. Question 1, chap 18, sect 4. part 1 of 1 10 points The small piston of a hydraulic lift has a crosssectional area of 4 . 2 cm 2 and the large piston has an area of 30 cm 2 , as in the figure below. 39 kN F 4 . 2 cm 2 area 30 cm 2 What force F must be applied to the small piston to raise a load of 39 kN? 1. 5061 . 22 N 2. 5279 . 49 N 3. 5460 N correct 4. 5647 . 06 N 5. 5865 N 6. 6057 . 45 N 7. 6249 . 25 N 8. 6446 . 51 N 9. 6658 . 33 N 10. 6875 N Explanation: Let : A 1 = 4 . 2 cm 2 , A 2 = 30 cm 2 , W = 39 kN , and F = F . According to Pascals law, the pressure ex erted on A 1 must be equal to the one exerted on A 2 . The pressure P 1 = F A 1 must be equal to the pressure P 2 = W A 2 due to the load. F A 1 = W A 2 , so F = A 1 A 2 W = (4 . 2 cm 2 ) (30 cm 2 ) (39000 N) = 5460 N . Question 2, chap 17, sect 3. part 1 of 1 10 points This picture shows the displacements S of the air molecules in a traveling sound wave as a function of distance, x . + A A S / 2 3 / 2 2 Sound Wave Which of the following tubes, open at the left end and open at the right end, is closest to the right length so as to resonate at its fundamental frequency when placed in this sound wave? 1. = 1 2 correct 2. = 1 4 3. = 3 8 4. = 1 8 5. = 3 4 6. = 3 2 midterm 04 BOBBITT, JAMES Due: May 2 2007, 11:00 pm 2 7. = 8. = 2 Explanation: The tube is open at the left end requiring an antinode in the wave form. The tube is open at the right end requiring an antinode in the wave form. The displaced between the antinode on the left and the antinode on the right is shown in the figure below. This correspondance can be represented by the distance between = 1 4 and = 3 4 as shown. + A A S / 2 3 / 2 2 Sound Wave So the length of a tube to produce the fundamental resonance should be = 1 2 . Second of four versions. Question 3, chap 16, sect 2. part 1 of 1 10 points A harmonic wave y = A sin[ k x t ] , where A = 1 meter, k has units of m 1 , has units of s 1 , and has units of radians, is plotted in the diagram below. +1 1 A (meters) x (meters) 6 12 18 At the time t = 0 Which wave function corresponds best to the diagram? 1. y = A sin bracketleftbiggparenleftbigg 2 15 m parenrightbigg x t parenleftbigg 2 3 parenrightbiggbracketrightbigg 2. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x t parenleftbigg 5 3 parenrightbiggbracketrightbigg 3. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x t parenleftbigg 4 3 parenrightbiggbracketrightbigg 4. y = A sin bracketleftbiggparenleftbigg 2 9 m parenrightbigg x t parenleftbigg 2 3 parenrightbiggbracketrightbigg 5. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x t...
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This note was uploaded on 09/14/2009 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Turner

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