Angry sound level = 70 db
Soothing sound level = 50 db
Frequency, f = 500 Hz
Assuming speed of sound = 345 m/s
Density (assumed) = 1.21 kg/m^3
Reference sound intensity, Io = 1*10^-12 w/m^2
Part (a): Initial sound intensity (angry sound)
10log (I/Io) = Sound level
Therefore,
For Ia = 70 db
Ia/(1*10^-12) = 10^(70/10)
Ia = 10^(70/10)*10^-12 = 1*10^-5 W/m^2
Part (b): Final sound intensity (soothing sound)
Is = 50 db
Therefore,
Is = 10^(50/10)*10^-12 = 18*10^-7 W/m^2
Part (c): Initial sound wave amplitude
Now,
I (W/m^2) = 0.5*A^2*density*velocity*4*π^2*frequency^2
Making A the subject;
A = Sqrt [I/(0.5*density*velocity*4π^2*frequency^2)]
Substituting;
A_initial = Sqrt [(1*10^-5)/(0.5*1.21*345*4π^2*500^2)] = 6.97*10^-8 m = 69.7 nm
Part (d): Final sound wave amplitude
A_final = Sqrt [(1*10^-7)/(0.5*1.21*345*4π^2*500^2)] = 6.97*10^-9 m = 6.97 nm
100 millimeters equals 0.1 meters.
Time period of fan (t) = 1 / 2 = 0.5 seconds
Angular velocity (ω)= 2π/t
ω = 4π
v = ωr
v = 4π x 0.61
v = 7.66 m/s
<span>The Ptolemaic theory of the universe was
disproved by Nicolaus Copernicus (1473–1543), letter C and followed by Johannes
Kepler (1571–1630). <span>Geocentric
theory suggested that the Sun and moon orbited Earth, and the rest of the
planets orbited the Sun is Heliocentric theory. Heliocentric theory of Nicolaus
Copernicus during the Scientific Revolution on 17th and 18th
century while Geocentric theory was proposed by Ptolemy (AD 150) and Aristotle.
Today, we believe more on the Heliocentric theory and it has been proven as
well.</span></span>
<span> </span>
