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Ratling [72]
3 years ago
9

A 0.71 W point source emits sound waves isotropically. Assuming that the energy of the waves is conserved, find the intensity (a

)1.4 m from the source and (b)2.6 m from the source.
Physics
1 answer:
sveticcg [70]3 years ago
5 0

Answer:

(a) 2.88×10⁻² W/m²

(b) 8.36×10⁻³ W/m²

Explanation:

The intensity of sound from an isotropic point source, with distance L is given as

I = P/(4πL²) .................................... Equation 1

Where I = intensity of sound, P = Power from the source, L = length, π = pie.

(a)

1.4 m from the source.

I = P/(4πL²)

Given: P = 0.71 W, L = 1.4 m, π = 3.14.

Substitute into equation 1

I = 0.71/(4×3.14×1.4²)

I = 0.71/24.6176

I = 0.0288 W/m².

I = 2.88×10⁻² W/m²

(b) 2.6 m from the source.

Given: P = 0.71 W, L = 2.6 m, π = 3.14

Substitute into equation 1

I = 0.71/(4×3.14×2.6²)

I = 0.71/84.9056

I = 0.00836 W/m²

I = 8.36×10⁻³ W/m²

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A classroom has 24 fluorescent bulbs, each of which is 32 W. how much energy does it take to light the room for a minute?(unit=J
cestrela7 [59]

Answer:

Energy= 46.08KJ

Explanation:

Given that the power needed to light each bulb is 32W

We know that Power = \frac{energy}{time}

The energy needed to light one bulb=power*time

Given time = 1minute = 60 seconds

Energy = 32W*60sec=1920J

Therefore energy needed to light one bulb is 1920J

The energy needed to light 24 bulbs = 1920*24 =46080J=46.08KJ

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3 years ago
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At standard temperature and pressure, carbon dioxide has a density of 1.98 kg/m3. What volume does 1.70 kg of carbon dioxide occ
nikitadnepr [17]

Answer:

<h2>volume= 0.85m^3</h2>

Explanation:

<em>The density of a substance is defined as the mass per unit volume of the substance, the unit is in kg/m^3 and it is represented by the greek letter rho</em>

Step one:

given data

we are told that the density  of Co2=  1.98 kg/m3

and the mass of Co2 is= 1.70 kg

we know the relation between mass, volume and density is

density=mass/volume

make volume subject of formula we have

volume=mass/density

substitute we have

volume=1.7/1.98\\\\volume= 0.85m^3

8 0
3 years ago
Bob, Jill, Kim, and Steve measure an object's length, density, mass, and brightness, respectively. Which student must derive a u
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3 years ago
Our Sun shines bright with a luminosity of 3.828 x 1025 Watt. Her energies
kifflom [539]

Answer:

a)   E = 1.58 10²¹ J , b) Oil = 4,236 107 liter ,  e)   T = 54.3 C

Explanation:

a) To calculate the energy that reaches Earth, let us combine that the power emitted by the Sun is distributed uniformly on a spherical surface

     I = P / A

     A = 4π r²

in this case the radius of the sphere is the distance from the Sun to Earth r = 1.5 10¹¹ m

     I = P / A

     I = P / 4π r²

let's calculate

     I = 3,828 10²⁵/4 pi (1.5 10¹¹)²

     I = 1.3539 10²W / m² = 135.4 W / m2

the energy that reaches the disk of the Earth is

    E = I A

the area of ​​a disc

    A = π r²

    E = I π r²

where r is the radius of the Earth 6.37 10⁶ m

     E = 135.4 π(6.37 10⁶)

     E = 1,726 10¹⁶ W

This is the energy per unit of time that reaches Earth

    t = 1 dai (24h / 1day) (3600s / 1h) = 86400 s

     

    E = 1,826 10¹⁶ 86400

     E = 1.58 10²¹ J

b) for this part we can use a direct proportions rule

      Oil = 1.58 10²¹ (1 / 37.3 10⁶)

      Oil = 4,236 10⁷ liter

c) to silence the surface temperature of the Earth we use the Stefan-Bolztman Law

       P = σ A e T⁴

       T = \sqrt[4]{P/Ae}

nos indicate the refect, therefore the amount of absorbencies

       P_absorbed = 0.7 P

let's calculate

       T = REA (0.7 1.58 1021 / [pi (6.37 106) 2 1)

       T = RER (8,676 106)

       T = 54.3 C

b) Among the other factors that must be taken into account is the greenhouse effect, due to the absorption of gases from the atmosphere

4 0
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