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3 years ago

Help with the two questions above? Correct answers?

Physics

1 answer:

LenKa [72]3 years ago

7 0

(6) first choice: the frequency appears higher and wavelength is shorter.

The car approaches a stationary observer and so the sound will appear to have shorter wavelength. This creates an effect of its siren to sound with higher frequency than it would do if both were stationary.

(7) The Doppler formula for frequency in the case of a stationary observer and source approaching it is as follows:

$f_O = \frac{v}{v-v_s}\cdot f= \frac{343\frac{m}{s}}{(343-25)\frac{m}{s}}\cdot 400Hz \approx 431Hz$

The wavelength is then

$\lambda = \frac{343\frac{m}{s}}{431Hz}\approx 0.80 m$

The third choice "0.80m; 431Hz" is correct

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A 477 g portion of soup is heated in a microwave oven from 25°C to 90°C, using radiation with a wavelength of 1.55 × 10⁻² m. Ass

zheka24 [161]

To solve this problem we will use the heat transfer equations, to determine the amount of heat added to the body. Subsequently, through the energy ratio given by Plank, we will calculate the energy of each of the photons. The relationship between total energy and unit energy will allow us to determine the number of photons

The mass of water in the soup is 477g

The change in temperate is

$\Delta T = (90+273K)-(25+273K) = 65K$

Use the following equation to calculate the heat required to raise the temperature:

$q = mc\Delta T$

Here,

m = Mass

c = Specific Heat

$q = (477)(4.184)(65)$

$q = 129724.92J$

The wavelength of the ration used for heating is $1.55*10^{-2}m$

The number of photons required is the rate between the total energy and the energy of each proton, then

$\text{Number of photons} = \frac{\text{Total Energy}}{\text{Energy of one Photon}}$

This energy of the photon is given by the Planck's equation which say:

$E = \frac{hc}{\lambda}$

Here,

h = Plank's Constant

c = Velocity of light

$\lambda =$ Wavelength

Replacing,

$E = \frac{(6.626*10^{-34})(3*10^8)}{1.55*10^{-2}}$

$E = 1.28*10^{-23}J$

Now replacing we have,

$\text{Number of photons} = \frac{82240.7}{1.28*10^{-23}}$

$\text{Number of photons} = 6.41*10^{27}$

Therefore the number of photons required for heating is $6.41*10^{27}$

4 0

3 years ago

7. A sound wave begins traveling through a thin metal rod at one end with a speed that is 15 times the speed of sound in air. If

san4es73 [151]

Answer:

L = 44,096 m

Explanation:

The speed of the sound wave is constant therefore we can use the relations of uniform kinematics

v = x / t

the speed of the wave in the bar is

v = 15 v or

v = 15 343

v = 5145 m / s

The sound at the bar goes the distance

L = v t

Sound in the air travels the same distance

L = v_air (t + 0.12)

as the two recognize the same dissonance,

v t = v_air (t +0.12)

t (v- v_air) = 0.12 v_air

t = 0.12 v_air / (v -v_air)

et's calculate

t = 0.12 343 / (5145 - 343)

t = 8.57 10-3 s

The length of the bar is

L = 5145 8.57 10-3

L = 44,096 m

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3 years ago

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kenny6666 [7]

Answer:

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3 years ago

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An 12 kg mass and a 18 kg mass experience a force of gravity pulling the balls towards each other of

Inessa [10]

Answer:

$5.5\:\mathrm{m}$

Explanation:

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$F=G\frac{m_1m_2}{r^2}$ ,

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Solving, we get:

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Calculate the pOH of this solution. <br><br> pH = 1.90 pOH = <br><br> right answer get brainliest

laila [671]

The answer is 12.10 pOH

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3 years ago

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