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kaheart [24]
3 years ago
15

A dish tv satellite dish is the shape of a paraboloid. the dish is 36 inches wide, and 8 inches deep. how many inches should the

receiver be located from the vertex for optimal reception? (round to the nearest thousandth)

Mathematics
1 answer:
MrRa [10]3 years ago
4 0
Refer to the diagram shown below. It shows a vertical cross-section of the paraboloid through its axis of symmetry.

Let the vertex of the parabola be at the origin. Then its equation is of the form
y = bx²

Because the parabola passes through (18,8), therefore
8 = b(18²)
b = 0.02469
The parabola is y = 0.02469x².

The receiver should be placed at the focal point of the paraboloid for optimal reception.
The y-coordinate of the focus is
a = 1/(4b) = 1/0.098765 = 10.125 in

Answer: The receiver is located at 10.125 inches from the vertex.

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Suppose that a spherical droplet of liquid evaporates at a rate that is proportional to its surface area: where V = volume (mm3
Alex

Answer:

V = 20.2969 mm^3 @ t = 10

r = 1.692 mm @ t = 10

Step-by-step explanation:

The solution to the first order ordinary differential equation:

\frac{dV}{dt} = -kA

Using Euler's method

\frac{dVi}{dt} = -k *4pi*r^2_{i} = -k *4pi*(\frac {3 V_{i} }{4pi})^(2/3)\\ V_{i+1} = V'_{i} *h + V_{i}    \\

Where initial droplet volume is:

V(0) = \frac{4pi}{3} * r(0)^3 =  \frac{4pi}{3} * 2.5^3 = 65.45 mm^3

Hence, the iterative solution will be as next:

  • i = 1, ti = 0, Vi = 65.45

V'_{i}  = -k *4pi*(\frac{3*65.45}{4pi})^(2/3)  = -6.283\\V_{i+1} = 65.45-6.283*0.25 = 63.88

  • i = 2, ti = 0.5, Vi = 63.88

V'_{i}  = -k *4pi*(\frac{3*63.88}{4pi})^(2/3)  = -6.182\\V_{i+1} = 63.88-6.182*0.25 = 62.33

  • i = 3, ti = 1, Vi = 62.33

V'_{i}  = -k *4pi*(\frac{3*62.33}{4pi})^(2/3)  = -6.082\\V_{i+1} = 62.33-6.082*0.25 = 60.813

We compute the next iterations in MATLAB (see attachment)

Volume @ t = 10 is = 20.2969

The droplet radius at t=10 mins

r(10) = (\frac{3*20.2969}{4pi})^(2/3) = 1.692 mm\\

The average change of droplet radius with time is:

Δr/Δt = \frac{r(10) - r(0)}{10-0} = \frac{1.692 - 2.5}{10} = -0.0808 mm/min

The value of the evaporation rate is close the value of k = 0.08 mm/min

Hence, the results are accurate and consistent!

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Circle R's sector is (5/2)² = 25/4 the area of Circle Q's sector.
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In 2010, the population of Kingsford was 8000. By 2014 the population had increased by 15% and 2/5 of the population was age 12
Anastasy [175]
<h2>Hello!</h2>

The answer is: The population age 12 or under was 3680.

<h2>Why?</h2>

If in 2010 the population of Kignsford was 8000, and by 2014 the population had increased by 15% we need to calculate the total population and then, calculate how many people was age 12 or under.

We must remember that we cannot work with percentage values, so, to make 15% a real number, we need to divide it by 100:

15(Percentage)=\frac{15}{100}=0.15

So,

Calculating the population by 2014, we have:

Population_{2014}=Population_{2010}+ Population_{2010}*0.15

Then, substituting we have:

Population_{2014}=8000+ 8000*0.15=9200

Now, calculating the population that was age 12 or under, knowing that it was 2/5 of the total population, we have:

Population=TotalPopulation*\frac{2}{5}\\\\Population=9200*\frac{2}{5}=3680

So, the population age 12 or under was 3680.

Have a nice day!

6 0
3 years ago
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