{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Homework_20

# Homework_20 - Nguyen Thanh Homework 20 Due 7:00 pm Inst D...

This preview shows pages 1–2. Sign up to view the full content.

Nguyen, Thanh – Homework 20 – Due: Nov 16 2007, 7:00 pm – Inst: D Weathers 1 This print-out should have 9 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points It is found that a 5 . 2 m segment of a long string contains 3 complete wavelengths and has a mass of 170 g. At one point it is vibrat- ing sinusoidally with a frequency of 51 Hz and a peak to valley displacement of 0 . 95 m. What power is being transmitted along the string? Correct answer: 33477 . 7 W. Explanation: Let : l = 5 . 2 m , λ = 5 . 2 m 3 , m = 170 g , f = 51 Hz , and A = 0 . 95 m 2 . Since k 2 π λ , ω 2 π f , v ω k , P = 1 2 μ ω 2 A 2 v = 1 2 m l · (2 π f ) 2 A 2 λ f = 1 2 170 g 5 . 2 m [2 π (51 Hz)] 2 × 0 . 95 m 2 2 5 . 2 m 3 (51 Hz) = 33477 . 7 W . keywords: 002 (part 1 of 2) 10 points A point source emits sound waves with an average power output of 0 . 907 W. Find the intensity 2 . 25 m from the source. Correct answer: 0 . 0142571 W / m 2 . Explanation: A point source emits energy in the form of a spherical waves. At a distance R from the source, the power is distributed over the surface area of a sphere, 4 πR 2 . Therefore, the intensity at a distance R = 2 . 25 m from the source is I = P av 4 π R 2 = 0 . 0142571 W / m 2 . 003 (part 2 of 2) 10 points Find the distance at which the sound reduces to a level of 69 dB. Correct answer: 95 . 3232 m. Explanation: We can find the intensity at the β = 69 dB level by using the equation β = 10 log I I 0 with I 0 = 1 × 10 - 12 W / m 2 : 69 dB = 10 log I 1 × 10 - 12 W / m 2 therefore I = 10 β/ 10 I 0 = 10 6 . 9 (1 × 10 - 12 W / m 2 ) = 7 . 94328 × 10 - 6 W / m 2 .

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 4

Homework_20 - Nguyen Thanh Homework 20 Due 7:00 pm Inst D...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online