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Unformatted text preview: homework 14 – ALIBHAI, ZAHID 1 Latest unpenalized work: Apr 30 2007 Mon day 04:00 (after this date you can not make a perfect score). Work cutoff: May 2 2007, 4:00 am. Question 1 part 1 of 2 10 points An ambulance is traveling north at 49 m / s and is moving towards a car that is traveling south at 26 . 5 m / s. The ambulance driver hears his siren at a frequency of 690 Hz. The velocity of sound is 330 m / s . Ambulance 49 m / s 26 . 5 m / s Police What wavelength does the driver of the car detect from the ambulance’s siren? Answer in units of m. Question 2 part 2 of 2 10 points At what frequency does the driver of the car hear the ambulance’s siren? Answer in units of Hz. Question 3 part 1 of 2 10 points The equation for the Doppler shift of a sound wave of speed v , reaching a moving detector, is f ′ = f parenleftbigg v ± v d v ∓ v s parenrightbigg , where v d is the speed of the detector, v s is the speed of the source, f is the frequency of the source, and f ′ is the frequency at the detec tor. In the numerator the + / − indicates when the detector is moving toward/away from the source. In the denominator the − / + indi cates when the source is moving toward/away from the detector. A train moving toward a detector at 25 m / s blows a 350 Hz horn. The velocity of sound is v sound = 343 m / s . What frequency is detected by a stationary train? Answer in units of Hz. Question 4 part 2 of 2 10 points What frequency is detected by a train moving toward the first train at a speed of 15 . 5 m / s? Answer in units of Hz. Question 5 part 1 of 1 10 points A police car is traveling at a speed v c to the left. A truck is traveling at a speed v t to the right. A wind is blowing in the opposite direction as that of the truck with a speed v w to the left. The frequency of the siren on the police car is f c . The speed of sound in air is v a . Let v o be the speed of the observer in the truck, and v c be the speed of the source , the police car. Police v c v t Truck v w wind What is the frequency f t heard by an ob server in the moving truck? 1. f t = v a + v t − v w v a + v c − v w f c 2. f t = v a − v t + v w v a + v c − v w f c 3. f t = v a + v t + v w v a − v c + v w f c 4. f t = v a + v t − v w v a − v c + v w f c 5. f t = v a − v t − v w v a + v c − v w f c 6. f t = v a + v t + v w v a + v c − v w f c 7. f t = v a − v t − v w v a − v c + v w f c 8. f t = v a − v t + v w v a − v c + v w f c homework 14 – ALIBHAI, ZAHID...
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