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Svetach [21]
2 years ago
10

The human ear canal is, on average, 2.5cm long and aids in hearing by acting like a resonant cavity that is closed on one end an

d open on the other. The length of the ear canal is partially responsible for our sensitivities to certain frequencies. Use 340m/s for the speed of sound when performing the following calculations.
(a) What is the first resonant frequency?

(b) What is the wavelength at second resonance?

(c) How does the first resonant frequency change if the ear canal is full of water? (increases, shortens, no change or decreases...?)

(d) At a listener's ear, the intensity of a conversation is 4×10−6W/m2 and a typical adult's ear has a surface area of 210×10−3m2. What is the power of the sound waves on the ear?

(e) Long-term exposure to loud noises can damage hearing. If a loud machine produces sounds with an intensity level of 110dB, what would the intensity level be if the intensity were reduced by a factor of 3?
Physics
1 answer:
balandron [24]2 years ago
5 0

Answer:

a)  f = 3400 Hz , b)  f5 = 17000 Hz , c) speed is much higher and the frequency is directly proportional to the speed so  the frequency increases

Explanation:

The resonance in a system with one end closed and the other open, we can find it because in the closed points we have nodes and in the open parts we have a maximum, so for this system we have the following resonances

 

    4L = λ                fundamental

    4L = 3 λ₃           third harmonic

    4L = 5 λ₅           fifth harmonic

   4L = (2n + 1)λ     general with n = 1, 2,3,

a) the speed of the wave is

              v = λ f

              f = v /λ

               

            λ₁ = 4L / 1

            λ₁ = 4 0.025 m

            λ₁ = 0.1 m

             f = 340 / 0.1

             f = 3400 Hz

b) the second resonance occurs for n = 5

           λ₅ = 4 0.025 / 5

           λ₅ = 0.02 m

           f5 = 340 / 0.02

           f5 = 17000 Hz

c) if the channel is full of water the speed of sound is v = 1436 m / s

     Since the speed is much higher and the frequency is directly proportional to the speed so  the frequency increases

d) The intensity is defined

            I = P / A

            P = I A

            P = 4.10-6 210.10-3

            P = 840 10-9 W

e) the intensity is β₁ = 110 if it is reduced by a factor of 3, Δβ = 110/3 = 36.67 f

The intensity of the system is now β₂ = 110 - 36.67 = 73.33  

We can calculate what the intensity reduction is

              β1 = 10 log (I1 / Io)

              β2 = 10 log (I2 / Io)

              β1 - β 2 = 10 [log (I1 / Io) - log (I2 / Io))

              β1 -β2 = 10 log (I1 / I2)

               I1 / I2 = 10 (β1-β2) / 10

Calculous

             I1-I2 = 10 (36.67 / 10)

             I1 / I2 = 4645

             I2 = 1/4645 I1

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IgorC [24]

Answer: The energy delivered to the toaster is 264.490KJ

Explanation:

Here is the complete question:

The resistance of a bagel toaster is 14 ?. To prepare a bagel, the toaster is operated for one minute from a 120-V outlet. How much energy is delivered to the toaster?

Step-by-step explanation:

Please see attachment below

7 0
2 years ago
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Dane is holding an 8 kilogram box 2 metres above the ground. How much energy is in the box's gravitational potential energy stor
9966 [12]

156.8 Joules of energy is in the box's gravitational potential energy store

<u>Explanation</u>:

<em>Given:</em>

Mass of the box Dane is holding = 8 Kilograms

Height at which Dane is holding the box above the ground= 2 metres

<em>To Find:</em>

Gravitational potential energy in the box=?

<em>Solution:</em>

gravitational potential energy is the work done per mass on a object to move that object from one fixed location to to another location against gravity.Its unit is joules or J

Thus  Gravitational potential energy is  represented as,

PE_g=mgh

where

PE_g is the gravitational potential energy

m is the mass

h is the height

g is the gravitational force( 9.8 m/s^2)

Now substituting the given values,

PE_g=8\times 9.8\times 2

PE_g=156.8 Joules

4 0
2 years ago
Two window washers, Bob and Joe, are on a 3.00 m long, 395 N scaffold supported by two cables attached to its ends. Bob weighs 8
WINSTONCH [101]

Answer:

- the forces on the left hand side is 1.038 kN

- the forces on the right hand side is 1.483 kN

Explanation:

Given the data in the question, as illustrated in the image below;

Length of the scaffold = 3 m

weight of the scaffold = 395 N

Weight of Bob = 805 N and stands 1 m from the left end

weight of washing equipment = 500N and on sits 2 m from the left end

Weight of Joe = 820 N and stand 0.500 m from the right end

so the force on the left cable will be;

T_{left = \frac{1}{3m}[ (805 N)( (3-1) m) + ( 395 N )( \frac{3}{2} m) + ( 500 N )(1m ) + ( 820 N)( 0.500m ) ]

T_{left =  \frac{1}{3m}[ 1610 + 592.5 + 500 + 410 ]

T_{left =  \frac{1}{3m}[ 3112.5 ]

T_{left =  1037.5 N

T_{left =  1.038 kN

Therefore, the forces on the left hand side is 1.038 kN

On the right hand side;

T_{Right =  ( 805 N + 395 N + 500 N + 820 N ) - 1037.5 N

T_{Right =  2520 N - 1037.5 N

T_{Right =  1482.5 N

T_{Right =  1.483 kN

Therefore, the forces on the right hand side is 1.483 kN

5 0
1 year ago
Which of the following statements cannot be supported by Kepler's laws of planetary motion?
gladu [14]

Answer:

The rotational speed of the four smallest planets can be determined using the rotational speeds of the four largest planets and their orbital periods.

Explanation:

Kepler's three laws are:

1) The orbits of the planets around the Sun are ellipses, with the Sun at one of the focii

2) A line connecting the Sun with each planet sweeps out equal areas in equal time intervals

3) The cube of the semi-major axis of the orbit of one planet is proportional to the square of its orbital period

There 3 laws help explaining the following statements:

- <em>A planet's distance from the sun will not be the same in six months. --> </em>using the 1st law. In fact, since the orbit is an ellipse (and not a circle), and the Sun is at one of the focii, the distance of the planet from the Sun keeps changing during the year.

-<em> A planet's speed as it moves around the sun will not be the same in six months. -</em>-> using the 2nd law. In fact, since the line connecting the Sun to the planet must cover equal areas in the same time interval, it follows that the speed of the planet cannot be constant during the year (it will be faster when closer to the sun and slower when far from the sun).

- <em>The average distance of Saturn can be calculated using the average distance of Neptune and the orbital period of both planets. </em>--> using the 3rd law. In fact, the ratio \frac{a^3}{T^2} (where a is the semi-major axis of the orbit and T the orbital period) is constant and it is the same for every planet orbiting the sun, so by knowing the data of Neptune and the orbital period of Saturn, it is possible to calculate Saturn's average distance.

Instead, the following statement:

<em>The rotational speed of the four smallest planets can be determined using the rotational speeds of the four largest planets and their orbital periods.</em>

Is not supported by any Kepler's law.

8 0
2 years ago
3. A 4.1 x 10-15 C charge is able to pick up a bit of paper when it is initially 1.0 cm above the paper. Assume an induced charg
Anni [7]

Answer:

\mathbf{1.51\times10^{-15}N}

Explanation:

The computation of the weight of the paper in newtons is shown below:

On the paper, the induced charge is of the same magnitude as on the initial charges and in sign opposite.

Therefore the paper charge is

q_{paper}=-4.1\times10^{-15}C

Now the distance from the charge is

r=1cm=0.01m

Now, to raise the paper, the weight of the paper acting downwards needs to be managed by the electrostatic force of attraction between both the paper and the charge, i.e.

mg=\frac{k_{e}q_{1}q_{2}}{r^{2}}

\Rightarrow W=mg

=\frac{9\times10^{9}\times(4.1\times10^{-15})^{2}}{0.01^{2}}

=\mathbf{1.51\times10^{-15}N}

6 0
2 years ago
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