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3 years ago

The intensity of a 70-dB whistle is quintupled. What is the new decibel level

1 answer:

7 0

Multiplying the power of any signal by 5 can be described as
an increase of 6.99 dB .

If the whistle blew at 70 dB initially, and its sound power became
multiplied by 5, and the whistle and the listener both stayed in
the same places, then the listener would tell you that the whistle
was now blowing at 76.99 dB .

(More likely, he would report "77 dB" as he held his ears and winced.)

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An insulated rigid tank initially contains 1.4-kg saturated liquid water and water vapor at 200°C. At this state, 25 percent of

Elan Coil [88]

Solution:

Mass of liquid water and water vapor in the insulated tank initially = 1.4 kg

Temperature = 200 °C

And 25% of the volume by liquid water is steam.

State 1

$m=\frac{V}{v}$

$m=m_f+m_g$

$1.4=\frac{0.25V}{v_f}+\frac{0.75V}{v_g}$

$1.4=\frac{0.25V}{1.1565 \times 10^{-3}}+\frac{0.75V}{0.1274}$ (taking the value of $v_g$ and $v_g$ at 200°C )

$V=6.304 \times 10^{-3}$

Now quality of vapor

$x=\frac{m_g}{m}$

$=3.377 \times 10^{-3}$

Internal energy at state 1 can be found out by

$u_1=u_f+xu_{fg}$

$=850.65+3.377\times10^{-3}\times 1744.65$

= 856.54 kJ/kg

After heating with the resistor for 20 minutes, at state 2, the tank contains saturated water vapor $v_2=v_g \text { and }\ x=1$

Tank is rigid, so volume of tank is constant.

$v_g=v_2=\frac{V}{m}$

$v_g=\frac{6.304\times 10^{-3}}{1.4}$

$v_g=4.502 \times 10^{-3} \ m^3 /kg$

Now interpolate the value to get temperature at state 2 with specific volume value to get final temperature

$T_2=360+(374.14-360)\left(\frac{0.004502-0.006945}{0.003155-0.006945}\right)$

= 369.11° C

Internal energy at state 2

$u_2=2154.9 \ kJ/kg$

Now power rating of the resistor

$P=\frac{m(u_2-u_1)}{t}$

$P=\frac{1.4(2154.9-856.54)}{20 \times 60}$

= 1.51 kW

6 0

3 years ago

Two everyday examples of a starting motion

Tasya [4]

Pushing, pulling is the answer

8 0

3 years ago

Why do electric fish need to force electric charges to move?

Anastasy [175]

The electric eel generates large electric currents by way of a highly specialized nervous system that has the capacity to synchronize the activity of disc-shaped, electricity-producing cells packed into a specialized electric organ. Hope this helps!! Good luck

3 0

3 years ago

What will be the pressure exerterd by the 0bject if 4000n is acting on an area of 50msqure

Ivahew [28]

<h3>Given, </h3>

Force,F = 4000 N

Area,a = 50 m²

Pressure = Force/Area

★ Putting the values in the above formula,we get:

$\sf \rightarrow \: pressure = \dfrac{4000}{50}$

$\sf \rightarrow pressure = 80 \: N {m}^{ - 2}$

7 0

3 years ago

With the frequency set at the mid-point of the slider and the amplitude set at the mid-point of the slider, approximately how ma

Alenkinab [10]

Answer:

The wavelength stays the same.

Explanation:

When the amplitude is increased, the wavelength stays the same.

Here the wavelength doesn't depend upon the amplitude.

4 0

3 years ago