A police in a siren car moving with a speed 20m/s chases a thief moving with a speed v. The police car sounds a frequency 300 Hz, and both of them move towards a stationary siren of frequency 400Hz. Find the speed of thr thief.
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Given A police in a siren car moving with a speed 20m/s chases a thief moving with a speed v. The police car sounds a frequency 300 Hz, and both of them move towards a stationary siren of frequency 400Hz. Find the speed of the thief.
Let f1 be the sound of police car and f2 be the stationery siren . So f1 = f2 since there is no sound.
f1 = 330 - v/330 - 20 x 300 and f2 = 330 + v /330 x 400
So 330 - v/330 - 20 x 300 = 330 + v/330 + v/330 x 400
990 - 3v/31 = 1320 + 4v/33
33(990 - 3v) = 31(1320 + 4v)
223 v = - 8250
v = 36.99 m/s
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