# oldhw 29 - alexander(jra2623 – oldhomework 29 – Turner...

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Unformatted text preview: alexander (jra2623) – oldhomework 29 – Turner – (92510) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points The area of a typical eardrum is about 5 . 5 × 10 − 5 m 2 . Find the sound power (the energy per sec- ond) incident on an eardrum at the threshold of hearing ( 1 × 10 − 12 W / m 2 ) . Correct answer: 5 . 5 × 10 − 17 W. Explanation: Let : A = 5 . 5 × 10 − 5 m 2 and I = 1 × 10 − 12 W / m 2 . At the threshold of hearing, I = P A P = I A = ( 1 × 10 − 12 W / m 2 )( 5 . 5 × 10 − 5 m 2 ) = 5 . 5 × 10 − 17 W . 002 (part 2 of 2) 10.0 points Find the sound power incident on an eardrum at the threshold of pain ( 1 W / m 2 ) . Correct answer: 5 . 5 × 10 − 5 W. Explanation: Let : I = 1 W / m 2 . At the threshold of pain, P = ( 1 W / m 2 )( 5 . 5 × 10 − 5 m 2 ) = 5 . 5 × 10 − 5 W . 003 10.0 points The length of a string is 86 . 4 cm, and it is fixed at each end. There is a standing wave on the string with wavelength 19 . 2 cm. Which figure schematically represents the standing wave? 1. 2. 3. 4. 5. 6. correct 7. 8. 9. Explanation: Let : L = 86 . 4 cm and λ = 19 . 2 cm ....
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oldhw 29 - alexander(jra2623 – oldhomework 29 – Turner...

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