14.X <?xml:namespace prefix = o ns = \"urn:schemas-microsoft-com:office:office\"

ID: 2109001 • Letter: 1

Question

14.X <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

James Bond is riding a bike at 15 m/s, chasing Car #1 moving in the same direction at 35 m/s.

Behind James is another car, Car 2, chasing him at 20 m/s. Both cars have horns blaring at a

frequency of 390 Hz. Assume a sound speed of 340 m/s.

a. What frequency does James hear from Car 1?

b. From Car 2?

c. What is the beat frequency he hears?

14.Y

Your roommate has two loud speakers on either end of your 5 meter long dorm room blaring a

mind-numbing bass tune at a constant 50 Hz. The desk where you study is at a point of constructive

interference somewhere along the line joining the two speakers. How far do you need to move your

desk to be located at a point of destructive interference? (Note: to help visualize the effect of having

speakers at opposite ends of the room with waves traveling opposite directions, check out this

animation: http://physics.uwyo.edu/~chip/Classes/PHYS1210/Slides/Day42/super3.gifâ€

Suppose now your room is located at the south pole on a cold day when the temperature is -100 C. Do

you need to move your desk farther, or less far:? and by how much? Show a computation to back up

your answer.

14.x.

A. Fjb =(340+15)/(340-35)*390 = 450 Hz

B. Fjb = (340-15)/(340+20)*390 = 350 Hz

C. Fb = 450 - 350 = 100 Hz

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