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Sliva [168]
3 years ago
10

Two friends whisper at a volume of 20 decibels. Later, they converse at a volume of 40 decibels.

Physics
2 answers:
ruslelena [56]3 years ago
6 0

Answer:

Explanation:

The sound intensity is given by:

I (dB) = 10 log(I/Io)

Where I is the intensity in W/m²

Io = 1.0 × 10⁻¹² W/m²

40 dB = 10 log\frac{I_2}{I_o} \Rightarrow I_2 = 10^4 \times 1.0 \times 10^{-12}W/m^2 = 10^{-8}W/m^2

20 dB = 10 log\frac{I_1}{I_o} \Rightarrow I_1 = 10^2 \times 1.0 \times 10^{-12}W/m^2 = 10^{-10}W/m^2

\frac{I_2}{I_1} = \frac{10^{-8}W/m^2}{10^{-10}W/m^2}=100

Thus, the conversation would have 100 times greater than the whisper.

Yuki888 [10]3 years ago
4 0
40 dB is 20 dB more power than 20 dB is. 20 dB more means 100 times as much.
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You create a ramp using two text books and a 0.50m board. Using a timer you determine that a cart can roll down the ramp in 0.55
ahrayia [7]

Answer:

The velocity of the cart at the bottom of the ramp is 1.81m/s, and the acceleration would be 3.30m/s^2.

Explanation:

Assuming the initial velocity to be zero, we can obtain the velocity at the bottom of the ramp using the kinematics equations:

v=v_0+at\\\\v^2=v_0^2+2ad

Dividing the second equation by the first one, we obtain:

v=\frac{v_0^2+2ad}{v_0+at}

And, since v_0=0, then:

v=\frac{2ad}{at}\\\\v=\frac{2d}{t}\\\\v=\frac{2(0.50m)}{0.55s}\\\\v=1.81m/s

It means that the velocity at the bottom of the ramp is 1.81m/s.

We could use this data, plus any of the two initial equations, to determine the acceleration:

v=v_0+at\\\\\implies a=\frac{v}{t}\\\\a=\frac{1.81m/s}{0.55s}\\\\a=3.30m/s^2

So the acceleration is 3.30m/s^2.

7 0
3 years ago
A section of a parallel-plate air waveguide with a plate separation of 7.11 mm is constructed to be used at 15 GHz as an evanesc
adell [148]

Answer:

the required minimum length of the attenuator is 3.71 cm

Explanation:

Given the data in the question;

we know that;

f_{c_1 = c / 2a

where f is frequency, c is the speed of light in air and a is the plate separation distance.

we know that speed of light c = 3 × 10⁸ m/s = 3 × 10¹⁰ cm/s

plate separation distance a = 7.11 mm = 0.0711 cm

so we substitute

f_{c_1 = 3 × 10¹⁰ / 2( 0.0711  )

f_{c_1 = 3 × 10¹⁰ cm/s / 0.1422  cm

f_{c_1 =  21.1 GHz which is larger than 15 GHz { TEM mode is only propagated along the wavelength }

Now, we determine the minimum wavelength required

Each non propagating mode is attenuated by at least 100 dB at 15 GHz

so

Attenuation constant TE₁ and TM₁ expression is;

∝₁ = 2πf/c × √( (f_{c_1 / f)² - 1 )

so we substitute

∝₁ = ((2π × 15)/3 × 10⁸ m/s) × √( (21.1 / 15)² - 1 )

∝₁ = 3.1079 × 10⁻⁷

∝₁ = 310.79 np/m

Now, To find the minimum wavelength, lets consider the design constraint;

20log₁₀e^{-\alpha _1l_{min = -100dB

we substitute

20log₁₀e^{-(310.7np/m)l_{min = -100dB

l_{min = 3.71 cm

Therefore, the required minimum length of the attenuator is 3.71 cm

6 0
3 years ago
Which of the following statements best describes earths mineral resources
bulgar [2K]
It is D, you can not replace minerals. This makes them valuable.
8 0
3 years ago
Read 2 more answers
A person just supports a mass of 20kg suspended from a rope.
Georgia [21]

Answer:

F = 200 N

Explanation:

Given that,

The mass suspended from the rope, m = 20 kg

We need to find the resultant force acting on the rope. The resultant force on the rope is equal to its weight such that,

F = mg

Where

g is acceleration due to gravity

Put all the values,

F = 20 kg × 10 m/s²

F = 200 N

So, the resultant force on the mass is 200 N.

7 0
3 years ago
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strojnjashka [21]

Answer:

the answer is b

Explanation:

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2 years ago
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