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2 years ago

15

A Jackhammer from 1 meter away produces roughly 100dB of sound. What is the sound pressure caused by the Jackhammer? Recall that

the loudness of a sound in decibels (dB) is given by the equation L=20log10(ppref) dB. Please help i'm so lost!!!

1 answer:

gregori [183]2 years ago

3 0

Answer:2

Step-by-step explanation:

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Which point on the y-axis lies on the line that passes through point C and is perpendicular to line AB?

SCORPION-xisa [38]

The question is incomplete! Complete question along with answer and step by step explanation is provided below.

Question:

Which point on the y-axis lies on the line that passes through point C and is perpendicular to line AB?

A. (-6, 0)

B. (0, -6)

C. (0, 2)

D. (2, 0)

The graph of the question is attached.

Answer:

The point is (x, y) = (0, 2)

The correct option is C.

Therefore, the point (0, 2) on the y-axis lies on the line that passes through point C and is perpendicular to line AB.

Step-by-step explanation:

From the given graph, the points A and B are

$(x_1, y_1) = (-2, 4) \\\\(x_2, y_2) = (2,-8) \\\\$

The slope of the equation is given by

$m_1 = \frac{-8 - 4 }{2 -(-2)} \\\\ m_1 = \frac{-12 }{2+2} \\\\m_1 = \frac{-12 }{4} \\\\m_1 = -3 \\\\$

We know that the slopes of two perpendicular lines are negative reciprocals of each other.

$m_2 = - \frac{1}{m_1}$

So the slope of the other line is

$m_2 = \frac{1 }{3} \\\\$

Now we can find the equation of the line that is perpendicular to the line AB and passes through the point C.

From the graph, the coordinates of point C are

$(x_1, y_1) = (6, 4)$

The point-slope form is given by,

$y - y_1 = m(x -x_1)$

Substitute the value of slope and the coordinates of point C

$y - 4 = \frac{1 }{3} (x - 6)\\\\$

To get the y-intercept, substitute x = 0

$y - 4 = \frac{1 }{3} (0 - 6) \\\\y - 4 = \frac{-6 }{3}\\\\y - 4 = -2\\\\y = 4 -2 \\\\y = 2 \\\\$

So, the point is

$(x, y) = (0, 2)$

The correct option is C.

Therefore, the point (0, 2) on the y-axis lies on the line that passes through point C and is perpendicular to line AB.

6 0

2 years ago

Zöe schedules advertising for a radio station. She must fill 12 minutes each hour with 30 second ads and 60 second ads. Zöe sold

PilotLPTM [1.2K]

I cannot see Zoe's work to explain the error, but the correct method of solving is listed:

x is the number of 30-second ads
y is the number of 60-second ads

x+y=12(60)=720 would be the first equation; this is because while the ads together make 12 minutes, the ad times are in seconds. This means we must multiply 12 by 60.

y=2x is the second equation

Our system is then
x+y=720
y=2x

We will use substitution to solve this. Plug 2x in place of y in the first equation:
x+2x = 720

Combine like terms:
3x = 720

Divide both sides by 3:
3x/3 = 720/3
x = 240

Substitute this value in for x in the second equation:
y=2(240)
y=480

8 0

2 years ago

Carolyn is using the table to find 360% of 15. What values do X and Y represent in her table? Percent Total 100% 100% 100% 20% 2

asambeis [7]

Answer: c

Step-by-step explanation:

Based on the percent breakdown of 360%.

100% 100% 100% 20%20%20%

15. 15. 15. 3. 3. 3.

100% is all of it, so 15. This is x.

20% of it would be calculated as 0.2 x 15 or 3. This is y.

7 0

2 years ago

Read 2 more answers

Russell has a collection of 1,200 pennies. Of these pennies, 25% are dated before 1980, 35% are dated from 1980 to 2000, and the

STatiana [176]

480 pennies.

25% are dated before 1980, therefore:
1200(total):100 = 12 (1%)
12(1%)x25 = 300 (25%)

35% are dated from 1980 to 2000, therefore:
12(1%)x35 = 420 (35%)

25% are dated before 1980, 35% are dated from 1980 to 2000 and the rest are dated after 2000.
25% + 35% = 60%.
300(25%) + 420(35%) = 720.
60% = 720.
100%-60% = 40%.
40% is the amount of pennies that are dated after 2000.

The total (100%) of the pennies is 1200.
We also know that 60% of the total (1200) is 720.

1200(100%) - 720(60%) = 480(40%).

Therefore, the amount of pennies dated after 2000 in Russell’s Collection is 480.

7 0

2 years ago

Suppose the time a child spends waiting at for the bus as a school bus stop is exponentially distributed with mean 7 minutes. De

Gala2k [10]

Answer:

The probability that the child must wait between 6 and 9 minutes on the bus stop on a given morning is 0.148.

Step-by-step explanation:

Let the random variable <em>X</em> represent the time a child spends waiting at for the bus as a school bus stop.

The random variable <em>X</em> is exponentially distributed with mean 7 minutes.

Then the parameter of the distribution is, $\lambda=\frac{1}{\mu}=\frac{1}{7}$ .

The probability density function of <em>X</em> is:

$f_{X}(x)=\lambda\cdot e^{-\lambda x};\ x>0,\ \lambda>0$

Compute the probability that the child must wait between 6 and 9 minutes on the bus stop on a given morning as follows:

$P(6\leq X\leq 9)=\int\limits^{9}_{6} {\lambda\cdot e^{-\lambda x}} \, dx$

$=\int\limits^{9}_{6} {\frac{1}{7}\cdot e^{-\frac{1}{7} \cdot x}} \, dx \\\\=\frac{1}{7}\cdot \int\limits^{9}_{6} {e^{-\frac{1}{7} \cdot x}} \, dx \\\\=[-e^{-\frac{1}{7} \cdot x}]^{9}_{6}\\\\=e^{-\frac{1}{7} \cdot 6}-e^{-\frac{1}{7} \cdot 9}\\\\=0.424373-0.276453\\\\=0.14792\\\\\approx 0.148$

Thus, the probability that the child must wait between 6 and 9 minutes on the bus stop on a given morning is 0.148.

6 0

2 years ago