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Serggg [28]
2 years ago
14

What is the sound level in a car when the intensity is 0.5 pW/m2?

Physics
2 answers:
Sholpan [36]2 years ago
5 0

Level of sound is given by equation

L = 10 Log \frac{I}{I_0}

here we know that

I = 0.5 pW/m^2

also the standard intensity of sound will be

I_0 = 1 pW/m^2

now we will use above equation

L = 10 Log\frac{0.5}{1}

L = -3.0 dB

So here it is no given option is correct as its level is coming - 3 dB

andreev551 [17]2 years ago
4 0

Answer: 1. C) 57 dB

2. A) 5.5 x 10^ -15 J

3. D) 1.4 m

4. D) 47 cm

5. A) 6.2 MHz

6. B) -18.2 dB

7. A) 2.8 uJ

8. C) 90 m

9. C) 511 W

10. C) 3.16 x 10^ -7 W/m^2

Explanation: 100% for quick check :)

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Water is leaking out of an inverted conical tank at a rate of 10,500 cm3/min at the same time that water is being pumped into th
satela [25.4K]

The tank has a volume of \dfrac\pi3R^2H, where H=6\,\rm m is its height and R=\dfrac d2=2\,\rm m is its radius.

At any point, the water filling the tank and the tank itself form a pair of similar triangles (see the attached picture) from which we obtain the following relationship:

\dfrac26=\dfrac rh\implies r=\dfrac h3

The volume of water in the tank at any given time is

V=\dfrac\pi3r^2h

and can be expressed as a function of the water level alone:

V=\dfrac\pi3\left(\frac h3\right)^2h=\dfrac\pi{27}h^3

Implicity differentiating both sides with respect to time t gives

\dfrac{\mathrm dV}{\mathrm dt}=\dfrac\pi9h^2\,\dfrac{\mathrm dh}{\mathrm dt}

We're told the water level rises at a rate of \dfrac{\mathrm dh}{\mathrm dt}=20\,\frac{\rm cm}{\rm min} at the time when the water level is h=2\,\mathrm m=200\,\mathrm{cm}, so the net change in the volume of water \dfrac{\mathrm dV}{\mathrm dt} can be computed:

\dfrac{\mathrm dV}{\mathrm dt}=\dfrac\pi9(200\,\mathrm{cm})^2\left(20\,\dfrac{\rm cm}{\rm min}\right)=\dfrac{800,000\pi}9\,\dfrac{\mathrm{cm}^3}{\rm min}

The net rate of change in volume is the difference between the rate at which water is pumped into the tank and the rate at which it is leaking out:

\dfrac{\mathrm dV}{\mathrm dt}=(\text{rate in})-(\text{rate out})

We're told the water is leaking out at a rate of 10,500\,\frac{\mathrm{cm}^3}{\rm min}, so we find the rate at which it's being pumped in to be

\dfrac{800,000\pi}9\,\dfrac{\mathrm{cm}^3}{\rm min}=(\text{rate in})-10,500\,\dfrac{\mathrm{cm}^3}{\rm min}

\implies\text{rate in}\approx289,753\,\dfrac{\mathrm{cm}^3}{\rm min}

4 0
3 years ago
Consider a 40,000 km steel pipe in the shape of a ring that fits snuggly all around the circumference of the Earth. We are heati
Tatiana [17]

Answer:

The Height is  H = 70.02 m

Explanation:

We are given that the

                         Initial length is  = 40000\ Km = 40,000 *10^{3} m

from what we are told in the question the circumference of the circle is = 40,000 Km

  This means that the Radius would be :

         Let C denote the circumference

      So  

               C = 2 \pi r

      =>     r = \frac{C}{2 \pi}

               r = \frac{40,000}{2 \pi } = \frac{40,000*10^{3}}{2 *3.142}  = 6.365*10^6 m

We are told that 1-meter bar of steel that increases its temperature by 1 degree C will expand 11*10^{-6} meters

Hence

       The final length would be

                            40000*10^3 *(T + \alpha  )

Where T is the change in  temperature  \alpha is the Coefficient of linear expansion for steel

  let L_{final} denote the final length

   So

        L_{final} =40000*10^{6} *[1+ 11*10^{-6}]

                  = 40000440 \ m

 Now the Height is mathematically represented as

         Height(H) \ = \frac{change \ in \ radius \ }{2 \pi}

                       = \frac{(40000440-40000*10^3)}{2*3.142}

                       = 70.02m

3 0
3 years ago
3.Felipe was enjoying the sunny day at the beach. He told his friend Carl that he was really
Sonja [21]

Felipe was enjoying the sunny day at the beach. He told his friend Carl that he was really  enjoying the warm feeling that he was getting as he sat in the Sun. Carl explained that the  electromagnetic radiation was responsible for this warm feeling. The electromagnetic spectrum which was responsible for making Felipe feel warm is

<u>Infrared rays</u>

Explanation:

  • Infrared radiation (IR), or infrared light, is a type of radiant energy that's invisible to human eyes but that we can feel as heat.
  • All objects in the universe emit some level of IR radiation, but two of the most obvious sources are the sun and fire.
  • Infrared radiation has a longer wavelength and lower frequency than visible light. Too much exposure can damage your eyes and skin. On a global scale, trapped infrared radiation contributes to global warming.
  • Most warm objects in our everyday experiences emit infrared, and half of the energy produced by the Sun is also infrared.
  • The primary source of infrared radiation is heat or thermal radiation. This is the radiation produced by the motion of atoms and molecules in an object.
3 0
3 years ago
Two point charges, A and B, are separated by a distance of 22.0 cm . The magnitude of the charge on A is twice that of the charg
REY [17]

Answer:

1.12×10⁻⁵ C and 2.24×10⁻⁵ C.

Explanation:

From coulomb's law,

F = kAB/r².............................. Equation 1

Where F = Force exerted by each charge, A = charge at point A, B = charge at point B, r = distance of separation between the points, k = constant of proportionality.

Given: F = 47 N, r = 22 cm = 0.22 m.

Constant: k = 9.0×10⁹ Nm²/C²

Let: B = q, the A = 2q.

Substituting these values into equation 1,

47 = 9.0×10⁹(q×2q)/0.22²

47 = 18×10⁹(q²)/0.0484

q² = (47×0.0484)/(18×10⁹)

q² = 0.126×10⁻⁹

q² = 1.26×10⁻¹⁰

q = √( 1.26×10⁻¹⁰)

q = 1.12×10⁻⁵ C

The charge at point A = 2q = 2× 1.12×10⁻⁵  = 2.24×10⁻⁵ C.

Hence the charges are 1.12×10⁻⁵ C and 2.24×10⁻⁵ C.

3 0
3 years ago
If you measure the current in a circuit and the voltage across the circuit, can you predict the
Nataly [62]

Answer:

Sure, you can.

Explanation:

» Record the ammeter reading and voltimeter reading as I and V respectively.

» Then, from ohm's law [ voltage is proportional to current ]

{ \rm{V \:  \alpha \:  I}}

» Input the constant of proprtionality, from ohm's law, resistance is constant [ R ≠ 0 ]

{ \rm{V = IR}}

  • V is voltage
  • I is current
  • R is resistance

{ \boxed{ \boxed{ \rm{ \:R  =  \frac{V}{I} \:  \:  }}}}

6 0
2 years ago
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