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aleksklad [387]
4 years ago
15

A train station bell gives off a fundamental tone of 500 Hz as the train approaches the station at a speed of 30.0 m/s. If the s

peed of sound in air is 339 m/s, what will be the apparent frequency of the bell to an observer riding the train?
Physics
1 answer:
TiliK225 [7]4 years ago
3 0

Answer:

548.5 Hz

Explanation:

We are given that

Frequency of source=500 Hz

Speed of train=30m/s

Speed of sound in air=339m/s

We have to find the frequency of the bell to an observer riding the train.

The apparent frequency for the listener

f=\frac{v_0}{v_0-v_s}f_1

Where f_1=Frequency of source

v_0=Speed of sound

v_s=Speed of source

Using the formula

The apparent frequency of the bell to an observer riding the train=\frac{339}{339-30}\times 500=548.5 Hz

Hence, the apparent frequency of the bell to an observer riding the train=548.5 Hz

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Physical properties of minerals graphic organizer
Nadusha1986 [10]
The answer is in the attachment
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4 0
3 years ago
A river has a steady speed 0.500 m/s. A student swims upstream a distance of1.00 km and swims back to the starting point. a) If
Ivahew [28]

Answer:

a) 33.6 min

b) 13.9 min

c)  Intuitively, it takes longer to complete the trip when there is current because, the swimmer spends much more time swimming at the net low speed (0.7 m/s) than the time he spends swimming at higher net speed (1.7 m/s).


Explanation:


The problem deals with relative velocities.

  • Call Vr the speed of the river, which is equal to 0.500 m/s
  • Call Vs the speed of the student in still water, which is equal to 1.20 m/s
  • You know that when the student swims upstream, Vr and Vs are opposed and the net speed will be Vs - Vr
  • And when the student swims downstream, Vr adds to Vs and the net speed will be Vs + Vr.

Now, you can state the equations for each section:

  • distance = speed × time
  • upstream: distance = (Vs - Vr) × t₁ = 1,000 m
  • downstream: distance = (Vs + Vr) × t₂ = 1,000 m

Part a). To state the time, you substitute the known values of Vr and Vs and clear for the time in each equation:

  • (Vs - Vr) × t₁ = 1,000 m
  • (1.20 m/s - 0.500 m/s) t₁ = 1,000 m⇒ t₁ = 1,000 m / 0.70 m/s ≈ 1429 s
  • (1.20 m/s + 0.500 m/s) t₂ = 1,000 m ⇒ t₂ = 1,000 m / 1.7 m/s ≈ 588 s
  • total time = t₁ + t₂ = 1429s + 588s =  2,017s
  • Convert to minutes: 2,0147 s ₓ 1 min / 60s ≈ 33.6 min

Part b) In this part you assume that the complete trip is made at the velocity Vs = 1.20 m/s


  • time = distance / speed = 1,000 m / 1.20 m/s ≈ 833 s ≈ 13.9 min

Part c) Intuitively, it takes longer to complete the trip when there is current because the swimmer spends more time swimming at the net speed of 0.7 m/s than the time than he spends swimming at the net speed of 1.7 m/s.

6 0
4 years ago
A nonconducting sphere is made of two layers. The innermost section has a radius of 6.0 cm and a uniform charge density of −5.0C
Leno4ka [110]

Answer:

a) E =0, b)   E = 1,129 10¹⁰ N / C , c)    E = 3.33 10¹⁰ N / C

Explanation:

To solve this exercise we can use Gauss's law

        Ф = ∫ E. dA = q_{int} / ε₀

Where we must define a Gaussian surface that is this case is a sphere; the electric field lines are radial and parallel to the radii of the spheres, so the scalar product is reduced to the algebraic product.

           E A = q_{int} /ε₀

The area of ​​a sphere is

          A = 4π r²

         E = q_{int} / 4πε₀ r²

         k = 1 / 4πε₀

         E = k q_{int} / r²

To find the charge inside the surface we can use the concept of density

        ρ = q_{int} / V ’

         q_{int} = ρ V ’

         V ’= 4/3 π r’³

Where V ’is the volume of the sphere inside the Gaussian surface

 Let's apply this expression to our problem

a) The electric field in center r = 0

     Since there is no charge inside, the field must be zero

          E = 0

b) for the radius of r = 6.0 cm

In this case the charge inside corresponds to the inner sphere

        q_{int} = 5.0  4/3 π 0.06³

         q_{int} = 4.52 10⁻³ C

        E = 8.99 10⁹  4.52 10⁻³ / 0.06²

         E = 1,129 10¹⁰ N / C

c) The electric field for r = 12 cm = 0.12 m

In this case the two spheres have the charge inside the Gaussian surface, for which we must calculate the net charge.

     The charge of the inner sphere is q₁ = - 4.52 10⁻³ C

The charge for the outermost sphere is

       q₂ =  ρ 4/3 π r₂³

       q₂ = 8.0 4/3 π 0.12³

       q₂ = 5.79 10⁻² C

The net charge is

     q_{int} = q₁ + q₂

     q_{int} = -4.52 10⁻³ + 5.79 10⁻²

     q_{int} = 0.05338 C

The electric field is

        E = 8.99 10⁹ 0.05338 / 0.12²

        E = 3.33 10¹⁰ N / C

8 0
3 years ago
A loudspeaker, mounted on a tall pole, is engineered to emit 75% of its sound energy into the forward hemisphere, 25% toward the
Naily [24]

Answer:

"0.049 W" is the correct answer.

Explanation:

According to the given question,

r = \sqrt{(3.5)^2+(2.5)^2}

  =\sqrt{8.5}

SL=85

As we know,

⇒  SL=10 \ log(\frac{I}{I_o} )

     85=10 \ log(\frac{I}{10^{-12}} )

      I=3.162\times 1^{-4} \ W/m^2

Now,

⇒  P_{front} = I(2\pi r^2)

               =(3.162\times 10^{-4})(2\pi\times 18.5)

               =0.0368 \ W

               =0.75 \ P

or,

                =0.049 \ W

7 0
3 years ago
If the car passes point A with a speed of 20 m/s and begins to increase its speed at a constant rate of at = 0.5 m/s2 , determin
IceJOKER [234]

Answer:

1.68 \frac{m}{s^2}

Explanation:

Please find the image for the question as attached file.

Solution -

Given -

First of all we will calculate the velocity at point C,

As per newton's third law of motion-

V_C^2 = V_A^2 + 2 a_t (S_C - S_A)\\

Substituting the given values in above equation, we get -

V_C^2 = 20^2 + 2*0.5*(100-0)\\V_C = 22.361 \frac{m}{s}

Now we will determine the radius of curvature for the curve shown in the attached image

Y = 16 - \frac{1}{625} X^2\\

Differentiating on both the sides, we get -

\frac{dy}{dx} = -3.2 (10^-3) X\\\frac{d^2y}{d^2x} =  -3.2 (10^-3)\\Curve = \frac{[1+(\frac{dy}{dx})^2]^{\frac{3}{2}}  }{\frac{d^2y}{d^2x}} \\Curve = 312.5meter

Acceleration on curved path

a = \frac{V_C^2}{Curve} \\a = \frac{22.361^2}{312.5} \\a= 1.60 \frac{m}{s^2}

Final acceleration

a_f = \sqrt{0.5^2 + 1.6^2} \\a_f = 1.68\frac{m}{s^2}

5 0
3 years ago
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