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enyata [817]
2 years ago
3

While the decibel scale can be used in many disciplines, we shall restrict our attention to its use in acoustics, specifically i

ts use in measuring the intensity level of sound. The Sound Intensity Level (measured in decibels) of a sound intensity (measured in watts per square meter) is given by Compute Damage to your hearing can start with short term exposure to sound levels around 115 decibels. What intensity is needed to produce this level
Physics
1 answer:
Xelga [282]2 years ago
3 0

Answer:

I = 0.316 W/m^2

Explanation:

In order to calculate the intensity required to produce a sound level of 115 decibels, you use the following formula:

B=10log(\frac{I}{I_o})   (1)

B: sound level = 115dB

I: intensity of the sound = ?

Io: Threshold of hearing = 10^-12 W/m^2

You solve the equation (1) for I, by using properties of logarithms:

B=log(\frac{I}{I_o})^{10}\\\\10^{B}=10^{log(\frac{I}{I_o})^{10}}\\\\10^B=(\frac{I}{I_o})^{10}\\\\I=I_o10^{B/10}

Finally, you replace the values of all parameters:

I=(10^{-12}W/m^2)10^{115/10}\\\\I=0.316\frac{W}{m^2}

The intensity that produces a sound level of 115 dB is 0.316 W/m^2

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Cylinder A is moving downward with a velocity of 3 m/s when the brake is suddenly applied to the drum. Knowing that the cylinder
Xelga [282]

Answer:

Incomplete question

Check attachment for the given diagram

Explanation:

Given that,

Initial Velocity of drum

u=3m/s

Distance travelled before coming to rest is 6m

Since it comes to rest, then, the final velocity is 0m/s

v=3m/s

Using equation of motion to calculate the linear acceleration or tangential acceleration

v²=u²+2as

0²=3²+2×a×6

0=9+12a

12a=-9

Then, a=-9/12

a=-0.75m/s²

The negative sign shows that the cylinder is decelerating.

Then, a=0.75m/s²

So, using the relationship between linear acceleration and angular acceleration.

a=αr

Where

a is linear acceleration

α is angular acceleration

And r is radius

α=a/r

From the diagram r=250mm=0.25m

Then,

α=0.75/0.25

α =3rad/sec²

The angular acceleration is =3rad/s²

b. Time take to come to rest

Using equation of motion

v=u+at

0=3-0.75t

0.75t=3

Then, t=3/0.75

t=4 secs

The time take to come to rest is 4s

7 0
2 years ago
Steam at 700 bar and 600 oC is withdrawn from a steam line and adiabatically expanded to 10 bar at a rate of 2 kg/min. What is t
Setler79 [48]

Answer:

Final temperature of the steam = 304.29 K = 31.14°C

Rate Entropy generation of the process should be 0 because no heat is transferred into or out of the system. And ΔS = Q/T = 0 J/K.

But 0.01 J/k.s was obtained though, which is approximately 0.

Explanation:

For an adiabatic system, the Pressure and temperature are related thus

P¹⁻ʸ Tʸ = constant

where γ = ratio of specific heats. For steam, γ = 1.33

P₁¹⁻ʸ T₁ʸ = P₂¹⁻ʸ T₂ʸ

P₁ = 700 bar

P₂ = 10 bar

T₁ = 600°C = 873.15 K

T₂ = ?

(700⁻⁰•³³)(873.15¹•³³) = (10⁻⁰•³³)(T₂¹•³³)

T₂ = 304.29 K = 31.14°C

b) Rate Entropy generation of the process should be 0 because no heat is transferred into or out of the system. And ΔS = Q/T

To prove this

Entropy of the process

dQ - dW = dU

dQ = dU + dW

dU = mCv dT

dW = PdV

dQ = TdS

TdS = mCv dT + PdV

dS = (mCv dT/T) + (PdV/T) =

PV = mRT; P/T = mR/V

dS = (mCv dT/T) + (mRdV/V)

On integrating, we obtain

ΔS = mCv In (T₂/T₁) + mR In (V₂/V₁)

To obtain V₁ and V₂, we use PV = mRT

V/m = specific volume

Pv = RT

R for steam = 461.52 J/kg.K

For V₁

P = 700 bar = 700 × 10⁵ Pa, T = 873.15 K

v₁ = (461.52 × 873.15)/(700 × 10⁵) = 0.00570 m³/kg

For V₂

P = 10 bar = 10 × 10⁵ Pa, T = 304.29 K

v₂ = (461.52 × 304.29)/(10 × 10⁵) = 0.143 m³/kg

ΔS = mCv In (T₂/T₁) + mR In (V₂/V₁)

m = 2 kg/min = 0.0333 kg/s, Cv = 1410.8 J/kg.K

ΔS = [0.03333 × 1410.8 × In (304.29/873.15)] + (0.03333 × 461.52 × In (0.143/0.00570)

ΔS = - 49.56 + 49.57 = 0.01 J/K.s ≈ 0 J/K.s

3 0
2 years ago
What force must be exerted on the master cylinder of a hydraulic lift to support the weight of a 2000-kg car (a large car) resti
Nataliya [291]

Archimedes principle states that

 

F1 / A1 = F2 / A2

F2 = (A2 / A1) * F1

 

Also, formula for the force is F = mg. Formula for the area of the cylinder is A = πr^2, therefore we get

 

F2 = (πr2^2 / πr1^2) * mg

 

Since the diameter of the cylinders are 2 cm and 24 cm, r1 = 12 and r2 = 1.

 

Substituting the values to the derived equation, we get

 

F2 = (π 1^2 / π 12^2) * 2400 * 9.8

F2 = 163.3333 N

 

 

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6 0
2 years ago
If you pull a resistant puppy with its leash in a horizontal direction, it takes 80 N to get it going. You can then keep it movi
netineya [11]

Answer:

The coefficient of static friction between the puppy and the floor is 0.7273.

Explanation:

The horizontal force applied to move the puppy from a steady state has to be greater than the force of static friction, after it is moving the force needs to be equal to be greater than the force of dynamic friction in order to maintain its movement. The force of static friction is given by:

F_s = \mu_s*N

Where F_s is the static friction force, \mu_s is the coefficient of static friction and N is the normal force. Since there's no angle on the flor the normal force is equal to the weight of the puppy, therefore, N = 110\text{ N}, to make the puppy moving we need to use a force of 80 N, therefore, F_s = 80 \text{ N}, so we can solve for the coefficient as shown below:

80 = \mu_s*110\\\mu_s = \frac{80}{110} = 0.7273\\

The coefficient of static friction between the puppy and the floor is 0.7273.

5 0
2 years ago
Which of the following exists around every object that has mass?
ICE Princess25 [194]

Answer:

A is the correct answer.

Explanation:

6 0
2 years ago
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