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max2010maxim [7]
3 years ago
5

As the drawing illustrates, a siren can be made by blowing a jet of air through 20 equally spaced holes in a rotating disk. The

time it takes for successive holes to move past the air jet is the period of the sound. The siren is to produce a 2338.6-Hz tone. What must be the angular speed ω (in rad/s) of the disk?
Physics
1 answer:
Aneli [31]3 years ago
4 0

Answer:

ω = 630.2663 = 630[rad/s]

Explanation:

Solution:

- We can tackle this question by simple direct proportion relation between angular speed for the disk to rotate a cycle that constitutes 20 holes. We will use direct relation with number of holes per cycle to compute the revolution per seconds i.e frequency of speed f.

                                  1rev(20 hole) -> 20(cycle)/rev  

                                        2006.2(cycle) -> f ?  

                              f = 2006.2/20 = 100.31rev at second  

- The relation between angular frequency and angular speed is given by:

                                 ω = 2πf

                                 ω = 2*3.14*100.31

                                 ω = 630.2663 = 630[rad/s]

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75/100 = (1-e^-(t/CR))

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.75 -1 = -e^-(t/CR)

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in order to remove the exponent, take logs on both sides  

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t/CR = -ln(0.25)

t = -CR x ln (0.25)

t = -(17.7 x 10^-12 x 975) x (-1.38629)

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Explanation:

The free body diagram is drawn below.

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Given:

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