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rodikova [14]
3 years ago
11

Suppose a large housefly 3.0 m away from you makes sound with an intensity level of 40.0 dB. What would be the sound intensity l

evel if there 1000 identical flies at that same distance?
Physics
1 answer:
melisa1 [442]3 years ago
5 0

Answer:

Explanation:

Let the intensity of the noise be represented by I

Given that

40dB = 10 log 10 ⁡ ( I /I•) ........ 1

I• is the lowest or threshold intensity of sound made.

I represents the intensity of the sound/ noise

The intensity of noise of 1000flies will be

β = 10 log 10 ⁡(1000I/I•)

Open up the bracket

β = 10 log 10(1000)+ 10 log 10(I/I•)

10 log 10(10^3)+10 log 10(I/I•)

3×10(10 log 10) +10 log 10(I/I•)

Recall, 10 log 10 = 1

30×1 + 10 log 10(I/I•).........2

Put equation 1 into 2

β =30+40

= 70db

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Answer:

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A car initially traveling at 17.1 mph comes to rest in 9.7s what was its acceleration in this time?
ra1l [238]

Answer:

a=-.78m/s^2

Explanation:

Δv=at

  • Δv is the difference in velocity before and after a given time.
  • a is the acceleration of the object during this time.
  • t is time

(v_f-v_i)=at is another way to write this equation.

  • The Δ symbol represents "the difference between the initial and final values of a magnitude or vector", so Δv=(v_f-v_i)

v_f-v_i=at\\\frac{at}{t}=\frac{v_f-v_i}{t}\\a=\frac{v_f-v_i}{t}

  • I rearranged this equation to solve for a, but this is a step that you don't need to take, it's just good to get in the habit of doing this.
  • Plug in the given values. Note that our final velocity is 0, because the car travels until at <em>rest</em>.

a=\frac{v_f-v_i}{t}\\a=\frac{(0)-[(17.1\frac{miles}{hour} )(\frac{hour}{3600s})(\frac{1609.34m}{mile})]}{9.7s}

  • Our initial velocity is in mph, something not in standard units, so if not changed, you will get an incorrect answer. What you need to do is cancel out the units your prior value had using division and multiplication, and at the same time multiply and divide the correct numbers and units into your equation. Or look up a converter.

a=\frac{(0)-[(17.1\frac{miles}{hour} )(\frac{hour}{3600s})(\frac{1609.34m}{mile})]}{9.7s}\\a=\frac{0m/s-7.6m/s}{9.7s} \\a=\frac{-7.6m/s}{9.7s}

  • if you converted correctly, your answer for v_f will be ≅ 7.6m/s.
  • Now divide. Notice that the units for acceleration are m/s^2 or <em>meters per second, per second</em>.

a=\frac{-7.6m/s}{9.7s}\\a=-.78m/s^2

  • Our final answer is <em>negative </em>because the car is <em>slowing down</em>. Do not square this answer as the square symbol only applies to the units, not the magnitude.
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Liula [17]

Answer: C. -12 newtons

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In the horizontal direction,

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In the vertical direction as well, net force is zero:

Force due to gravity + force exerted by the ground = 0

12 N + force exerted by the ground = 0

⇒force exerted by the ground = 0 -12 N = -12 N

Thus, the correct option is C. -12 N where negative sign means that the direction of the force due to ground is opposite to the force of gravity.

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Answer:

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