1.the howler monkey is the loudest land animal and can be heard up to a distance

Question

1.the howler monkey is the loudest land animal and can be heard up to a distance of 1.9km. assume the acoustic output of a howler to be uniform in all directions. the distance at which the intensity level of a howler's call is 48dB,in SI units, is closest to :
a. 11
b.9.1
c. 7.6
d.13
e.15
2. at time t =0s, a wheel has an angular displacement of zero radians and an angular velocity of +24rad/s . the wheel has a constant acceleration of -0.43 rad/s2. in this situation the maximum value of the angular displacement in rad is closest to:
a. +1340
b.+670
c.+837
d. +1172
e.+1005

Explanation / Answer

1) Using the equation

beta= 10dB*log(I/Io)

Io is the reference intensity = 10^-12 W/m^2

beta = 48 dB

then 48dB = 10dB*log(I/10^-12)

4.8 = log(I/10^-12)

I = 6.3*10^-8 W/m^2

using the relation I1*r1^2 = I2*r2^2

10^-12*(1.9*1000)^2 = 6.3*10^-8*r2^2

r2 = 7.6 m

so correct choice is C) = 7.6 m

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2) given that theta_o = 0 rad

wi = 24 rad/sec

alpha = -0.43 rad/s^2

using kinematic equation

w^2 -wi^2 = 2*alpha*(theta-theta_o)

0^2 - 24^2 = -2*0.43*(theta-0)

theta = 670 rad

so the answer is b.670 rad

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