At rest, a car\'s horn sounds the note A (440 Hz). The horn is sounded while the

Question

At rest, a car's horn sounds the note A (440 Hz). The horn is sounded while the car is moving down the street. A bicyclist moving in the same direction with one-sixth the car's speed hears a frequency of 411 Hz.

(a) What is the speed of the car? (Assume the speed of sound in air is 343 m/s.)
m/s

2) An alert physics student stands beside the tracks as a train rolls slowly past. He notes that the frequency of the train whistle is 441 Hz when the train is approaching him and 426 Hz when the train is receding from him. Using these frequencies, he calculates the speed of the train. What value does he find? (Assume the speed of sound in air is 343 m/s.)

_________m/s

3)(a) Calculate the absolute pressure at the bottom of a fresh-water lake at a depth of 29.8 m. Assume the density of the water is 1.00 103 kg/m3 and the air above is at a pressure of 101.3 kPa.

_______pa

(b) What force is exerted by the water on the window of an underwater vehicle at this depth if the window is circular and has a diameter of 32.0 cm?

_______N

Explanation / Answer

Question 1) Given , Real frequency , f= 440 Hz

Apprent frequency f ' = 411 Hz

Let, the speed of car = v

It is given that speed of bicyclist v ' = v/6

Speed of sound V = 343 m / s

a) Using the formula for apparet frequency

f ' = [(V - v')/(V - v)] *f

440 = [ (343 - (v/6) ) / ( 343 - v) ] *411

(343 - (v/6)) / (343 - v) = 1.07

343 - (v/6) = 367.2 - 1.07v

0.9v = 24.2

v = 24.2/0.9 = 26.889 m/s

The speed of the car v = 26.889m / s

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