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Cloud [144]
3 years ago
8

A surface receiving sound is moved from its original position to a position three times farther away from the source of the soun

d. The intensity of the received sound thus becomes
a. three times as high,
b. nine times as high.
c. nine times as low.
d.three times as low.
Physics
1 answer:
vazorg [7]3 years ago
6 0

Answer:

c. nine times as low.

Explanation:

Sound intensity is defined as the acoustic power transferred by a sound wave per unit of normal area to the direction of propagation:

I\propto \frac{1}{A}

Since the sound wave has a spherical wavefront of radius r, then the area is given by:

A=4\pi r^2

Here r is the distance from the source of the sound. Thus sound intensity decreases as:

I\propto \frac{1}{4\pi r^2}\\\\I'\propto \frac{1}{4\pi r'^2}\\\\I'\propto \frac{1}{4\pi (3r)^2}\\\\I'\propto \frac{1}{9} \frac{1}{4\pi r^2}\\\\I'\propto \frac{1}{9} I

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Each blade of a fan has a radius of 11 inches. If the fan’s rate of turn is 1440o /sec, find the following. (a) The angular spee
notka56 [123]

Answer:

a) 24.43 radians per second

b) 268.73 inches per second

Explanation:

a) The angular speed of the fan on Celsius degrees/second is 1400, so we should convert that value to radians using the fact that 2π rad = 360 °C:

\omega = 1400\frac{C}{s}=1400\frac{C}{s}*\frac{2\pi\,rad}{360\,C}

\omega = 1400\frac{C}{s}=24.43\frac{rad}{s}

b) Linear speed on a point of the blade is related with angular speed of the fan by the equation

v=\omega r

with v linear speed, ω angular speed and r the radius of the blades. So:

v=(24.43\frac{rad}{s})(11 in)

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v=268.73\frac{in}{s}

3 0
3 years ago
How much mass should be attached to a vertical ideal spring having a spring constant (force constant) of 39.5 n/m so that it wil
mrs_skeptik [129]
The frequency of a simple harmonic oscillator such as a spring-mass system is given by
f= \frac{1}{2 \pi}   \sqrt{ \frac{k}{m} }
where 
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Re-arranging the formula, we get:
m= \frac{k}{4 \pi^2 f^2}
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we can find the value of the mass attached to it:
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7 0
3 years ago
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Answer:

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Explanation:

m = mass of the sled = 125 kg

v₀ = initial speed of the sled = 8.1 m/s

v = final speed of sled = 0 m/s

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d = stopping distance for the sled

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Answer: (b) direct object

Explanation:

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