help me, physics word problems suck?

Question

a siren can be made by blowing a jet of air through twenty 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 2200 Hz tone. what must be the angular speed in rad/s of the disk? please give me step by step, not just the answer. thanks.

Answer 1

If I understand correctly, one revolution of the disk is equal to one period. You need to know the time (T) taken for one period.

Frequency (f):
f = 1/ T
T = 1/ f
T = 1/ 2200
T = 0∙000 454 545....
T ≈ 454∙454 µs

Angular speed (w):
w = Θ/ t
w = 2π/ 454∙454 x 10^-6
w = 6∙283 185 307.../ 454∙454 x 10^-6
w = 13823∙007 68...
w ≈ 13,823 rad/s

If the period is 20 for one cycle then:
w ≈ 13,823 / 20 rad/s
w ≈ 691∙15 rad/s

Answer 2

Not sure what you don't understand, but here is how I would look at it.

1) Want to know the angular speed of the disk.
2) The angular speed is that speed at which 20 equally spaced holes produce a 2200 Hz tone.
3) The period of the sound is the time it takes for successive holes to pass over the jet. The period of a 2200 Hz tone is 4.55 E-4 seconds.
4) Since there are 20 holes in the disk, the period of rotation of the disk must be 20x this or 9.09 E-3 sec.
5) Therefore the disk rotates at 110 rev/sec
6) That is 691 rad/sec.

Answer 3

First work out the period of the tone:

T = 1/f = 1/2200 = .45msec

Now there are 20 equally spaces holes. So angular distance between holes is 2(Pi)/20 = (Pi)/10 radians.

This angular distance must be covered in .45msec. So

omega = (ang. distance) / time = (Pi/10) / .45 msec =
(f Pi) / 10 = 220 Pi = 691 rads/sec

Answer 4

The preliminary velocity upward, the only significant bit is a hundred and fifty sin sixty 5.0°. we are able to forget with regard to the horizontal, a hundred and fifty cos sixty 5.0° bit. Now, d = ½at^2 and v = at. So t = v/a and ½a(v/a)^2 = ½v^2/a = d. Or h in our case. So h = ½(150sin65.0°)^2/9.eighty one = 942 meters Edit: significant figures.