a sretchcl string Which osc of dee following pvrerlies s 43. A periodic wave is

Question

a sretchcl string Which osc of dee following pvrerlies s 43. A periodic wave is prockuced ou no selited u the specd of the wawe a) equency t) period (e) uasion in the string Ib) amplitude (d) wwelengh Decibele 44. A person is salking in a small rcs: and the sourd asten sity level s 60 dR everywhere vithin level? the room. if there ane cieht jesgle talking sinatimsously in the mxem, wh theunsd iniznsiry How much workis done in moring a charoe oi 3-0 A 3J against a vonage of 15 V? - C 15J D45 J 46. The speed iv) et which sound travels throagh sir is dependemi upen the temperature of the air and sens to follow she equatio remperanare of the air. D etemine the speed of sound under the falloowing conlitieis on a cald day whenthe orilar ietnieatriat h. insde the schoal where the tempenaure is 24 C ...on a war m day when the uudoor temperntere is 38 C a. 333, 345,383 b. 33. 3X4, 345-e345, 333, 354 d. 345. 30,375 e. 333, 345, 354 32

Explanation / Answer

44)

If the sound spreads uniformly in all directions and there are no reflections, you can assume that intensity (i.e. power per unit area) varies inversely with the square of the distance from the source. So quadrupling the distance causes the intensity to fall to 1/8 of its original level. The dB change is 10*log(1/8) = -9.030dB.

Assuming everyone makes an equal intensity contribution, the intensity ratio is 8, so the increase in dB is 10*log(8) = 9.030dB. Add this to 60 to get 69.03dB.

so the answer is C. 69dB.

45) Potential difference V = Workdone / charge

W = V * Q

= 15 *3

= 45 J

so d. 45J is the answer.

  

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