Question

Question 5 [6 marks] Two cars move directly away from one another. One car sounds a horn whose frequency is 486 Hz and a person in the other car hears a frequency of 473 Hz. The speed of sound is 343 m/s. The car which sounds its horn is moving twice as fast as the other car. What is the speed of the slower car? [6 marks] Question 6 [5 marks] When an open metal pipe is cut into two pieces, the lowest resonance frequency for the air column in one piece is 256 Hz and that for the other is 440 Hz. (Take speed of sound = 343 m/s) a) How long was the original pipe? [3 marks) b) What resonant frequency would have been produced by the original length of pipe? [2 marks] Question 7 [8 marks] The charges 41 = 2.0 x 10-7C, 92=-4.0 x 10-7C, and q3=-1.0 x 10-7C are placed at the corner of the triangle shown below. 3.0 m 5.0 m 4.0 m 92 What is the net force on qı? (8 marks)

Answer 1

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D are Here both the some and observer moving away from one another By Doppler effect, the apparent fequency V-Vo f'- f Vt Vs. . Given V = 2V0 473 H2= = 486 Hz x 3 43 m/s - vo 1343 m/s tavo 473 34 3 m/s - Vo 486 343m/stavo 162239 m/s + 9 4 6V0 = 166698-486 V7 1432 = 4459 Vo = 4459 1432 3.11 m/s speed of slower car is 3.11 m/s Sam

a ) For lowest resonance frequency N/A € 14 4 / L = 1 V=fi x= v 2f f L = V length of one piece) 재 2₂=V Llength of second piece) 2f2 Total length =htla / / - [ + 34,3 mln + b) = 343m/ 256HZ 440HZ 1.06m Resonance of onsinal pipe L= V २

f = V 2L 343 m/s 2x106m - 161.8 Hz x 162 Hz 7 For a the change direction of force is same as the electric field due to the causins charge. o= tan (3/4) 36.87° I Fid = kpulla31 (03) Fax Fray Fiz 5m 3m 9x10Nm / 6x2x10cxixido (3m)? 2x10 N 93 4m พน

13 + 12 = 2x105 (²) W Fil- k 19,921 - 7 -7 9x10 x 2x10 cх4x10c (5m) ² 2.88x 10-BN F2 -C2.88x1bCos 36.9 Đî +2.88x īó sin 36-83)- 2.3x105, " + 1.73x. 108 - 3) N fret = F 12 + E (f) = 2.3x10 + (1.73 + 2) + 10 3. 73x10N Fnet-5 (2.3x1080) + (-3.73x105N -59 = 2.3x10 i - 4.38X10N