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Evgesh-ka [11]
3 years ago
13

Suppose that a public address system emits sound uniformly in all directions and that there are no reflections. The intensity at

a location 26 m away from the sound source is 3.0 × 10-4 W/m2. What is the intensity at a spot that is 71 m away?
Physics
1 answer:
dybincka [34]3 years ago
5 0

Answer:

The intensity at a spot 71 m away is 4.02*10^{-5}  Wm^{-2}

Explanation:

Given:

Initial intensity,I_{1}=3.0*10^{-4} Wm^{-2} at a distance, d_{1} = 26 m

Required:

New intensity, I_{2} =? at a distance, d_{2} = 71 m

Using the inverse square law,

I ∝ \frac{1}{d^{2} }

⇒I_{1}I_{1}d_{1}^{2}  =I_{2}d_{2}^{2}

I_{2} =\frac{I_{1} d_{1}^{2}  }{d_{2}^{2}} =\frac{3.0*10^{-4}*26^{2}  }{71^{2} } \\×

I_{2}=4.02*10^{-5}  Wm^{-2}

Thus, the intensity at a spot that is 71 m away is 4.02*10^{-5}  Wm^{-2}

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Hydroelectricity provides about 7 percent of the electricity generated in the united states. (a) explain how a hydroelectric pow
aivan3 [116]

a. A dam is usually built at the site of hydroelectric power. As water accumulates, its potential power for producing electric power increases. As this water moves downstream from the dam, mostly through a fall, its kinetic energy is harnessed by turbines and converted to electric energy.


b. One factor is the height of the fall of the water from the dam. The higher the height the higher the kinetic energy of the water and hence can be converted to higher electric energy. The higher the number of coils of the turbine generator being rotated by the water, the higher the conversion to electric current.


c. One is impoundment. This type is the most common and involves the building of a dam to store water and later the water is released to turn turbines. The second type is diversion. This type does not require a dam. Some water is diverted from the main river to create a pen-stock that runs a turbine.


d. The advantage of hydroelectric power is that is is a clean energy source hence does not cause global warming. Global warming can have economic consequences. The operating cost of this type of plant is low hence the costs of electricity are able to be kept low for the consumers. 2 disadvantage is that creating a dam upstream causes a change in the physical and chemical characteristics of the river or water bodies affecting ecosystems. Another is that electricity is dependent on the water regime hence dependency is tied to climate.


4 0
3 years ago
A snail is at the bottom of a well, 115 feet deep. On day 1, it starts climbing up the side. That night it rests and slips down
julia-pushkina [17]

Answer:

Number of days needed = 57

Explanation:

Depth of well = 115 feet

Distance traveled in day = 3 feet up

Distance traveled in night = 1 feet down.

Total displacement in 1 day = 3 - 1 = 2 feet up

When the snail reaches 112 feet up, the next 3 feet up motion on day will make it reach the top.

\texttt{Days to travel 112 feet up = }\frac{112}{2}=56

After 56 days the displacement of snail is 112 feet.

On the next day it moves up by 3 feet and reaches out of well.

Number of days needed = 57

4 0
3 years ago
What speed should a satellite of mass 4,900 kg moving around
Rudiy27

Based on the calculations, the speed required for this satellite to stay in orbit is equal to 1.8 × 10³ m/s.

<u>Given the following data:</u>

  • Gravitational constant = 6.67 × 10⁻¹¹ m/kg²
  • Mass of Moon = 7.36 × 10²² kg
  • Distance, r = 4.2 × 10⁶ m.

<h3>How to determine the speed of this satellite?</h3>

In order to determine the speed of this satellite to stay in orbit, the centripetal force acting on it must be sufficient to change its direction.

This ultimately implies that, the centripetal force must be equal to the gravitational force as shown below:

Fc = Fg

mv²/r = GmM/r²

<u>Where:</u>

  • m is the mass of the satellite.
  • M is mass of the Moon.

Making v the subject of formula, we have;

v = √(GM/r)

Substituting the given parameters into the formula, we have;

v = √(6.67 × 10⁻¹¹ × 7.36 × 10²²/4.2 × 10⁶)

v = √(1,168,838.095)

v = 1,081.13 m/s.

Speed, v = 1.8 × 10³ m/s.

Read more on speed here: brainly.com/question/20162935

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8 0
2 years ago
Which option describes the direction of thermal energy transfer in Earth's
Montano1993 [528]

.........

Explanation:

Option B..... ...

4 0
3 years ago
Read 2 more answers
What will be the final temperature if a 4.00 g silver ring at 41.0◦C if it gives off 18.0 J of heat to the surroundings? The spe
Eduardwww [97]

Answer:

Final temperature, T_f=21.85^{\circ}

Explanation:

Given that,

Mass of silver ring, m = 4 g

Initial temperature, T_i=41^{\circ}C

Heat released, Q = -18 J (as heat is released)

Specific heat capacity of silver, c=0.235\ J/g\ C

To find,

Final temperature

Solution,

The expression for the specific heat is given by :

Q=mc\Delta T

Q=mc(T_f-T_i)

T_f=\dfrac{-Q}{mc}+T_i

T_f=\dfrac{-18}{4\times 0.235}+41

T_f=21.85^{\circ}

So, the final temperature of silver is 21.85 degrees Celsius.

5 0
3 years ago
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