Sound at 70 dB is 70 dB louder than the human reference level. That's 10⁷ times as much as the reference sound power.
Sound at 73 dB is 73 dB louder than the human reference level. That's 10⁷.³ or 2 x 10⁷ times as much as the reference sound power.
Sound at 80 dB is 80 dB louder than the human reference level. That's 10⁸ or 10 x 10⁷ times as much as the reference sound power.
Now we can adumup:
Intensity of all 3 sources = (10⁷) + (2 x 10⁷) + (10 x 10⁷)
Intensity = (13 x 10⁷) times the sound power reference intensity.
Intensity in dB = 10 log (13 x 10⁷) = 10 (7 + log(13)
Intensity = 70 + 10 log(13)
Intensity = 70 + 10 (1.114)
Intensity = 70 + 11.14
Intensity = <em>81.14 dB</em>
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Looking at the questioner's profile, I seriously wonder whether I'll ever get a comment in return from this creature, and how I'll ever find out if my solution is correct. For that matter, I'm also seriously questioning how and whether my solution will ever be used for anything.
Temperature. X-axis is always the independent variable.
I can’t see the picture what do you need help with
Answer: -49m/s.
Explanation:
As the rock only falls, we will assume that the initial vertical velocity is zero.
We neglect the air friction, so the only force acting on the rock is the gravitational force, this means that the acceleration is -g = -9.8m/s^2.
Then we can write:
a(t) = -9.8m/s^2
To write the velocity of the rock, we must ingrate over time and get:
v(t) = (-9.8m/s^2)*t + v0
where v0 is the initial vertical velocity, and as we said above, v0 = 0m/s
Then the vertical velocity as a function of time is:
v(t) = (-9.8m/s^2)*t
Now, the question is:
"...If a rock falls for 5 seconds near the surface of the earth and with no air friction, it will reach a velocity of..."
Then we need to evaluate the velocity equation in t = 5 seconds.
v(5s) = (-9.8m/s^2)*5s = -49m/s.
