QTest #9-solutions - Version 126/ABDDC QTest #9 Antoniewicz...

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Unformatted text preview: Version 126/ABDDC QTest #9 Antoniewicz (57420) 1 This print-out should have 4 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Two wires made of the same material are stretched by equal forces. The second wire is twice as long as the first one and also has twice the diameter of the first wire. If the first wire is stretched by 5 . 2 cm , then by how long is the second wire stretched? 1. 4.05 2. 2.6 3. 0.7 4. 4.5 5. 3.5 6. 4.1 7. 1.65 8. 2.0 9. 3.25 10. 3.45 Correct answer: 2 . 6 cm. Explanation: Let : L 1 = 5 . 2 cm , L 2 = 2 L 1 , and r 2 = 2 r 1 . Youngs modulus is Y = F L A L = F L r 2 L Y F = L r 2 L . The forces are the same, so L 1 r 2 1 L 1 = L 2 r 2 2 L 2 L 2 = L 2 L 1 parenleftbigg r 1 r 2 parenrightbigg 2 L 1 = 2 parenleftbigg 1 2 parenrightbigg 2 L 1 = 1 2 L 1 = 1 2 (5 . 2 cm) = 2 . 6 cm ....
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This note was uploaded on 05/02/2011 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.

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QTest #9-solutions - Version 126/ABDDC QTest #9 Antoniewicz...

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