Answer
(MG-24)
I pretty sure this the answer your looking for
<span>Even in space, there is still presence of gravity. The
cause of weightlessness is not how far above the earth the space shuttle is but
rather how fast it is travelling. The shuttle is in free fall causing
weightlessness, but it is travelling fast enough to miss the earth as it falls.
Similarly, the airplane could also provide weightlessness if it went free fall
as well. However, that ends as the plane hits the ground. </span>
A) experimental because he isn’t sure and is testing out
Answer:
a) I₂ = 2.78 10⁻² W / m²
, b) I₃ = 9 10⁻² W/m²
, c) R₄ = 2 10⁶ m
Explanation:
The intensity of a wave is defined as the emission power per unit area
I = P / A
The unit of decibels is defined by
β = 10 log (I / Io)
With Io the hearing threshold 10⁻¹² W / m²
a) the intensity at r = 12m
Let's use the first equation
P = IA
I₁ A₁ = I₂ A₂
Let's look for intensity (I₁)
β / 10 = log I₁ / I₀
I / I₀ =
I = I₀
I = 1 10⁻¹²
I = 1 W / m²
The area of a spherical surface is
A = 4π R²
I₁ r₁² = I₂ r₂²
I₂ = I₁ R₁² / r₂²
I₂ = I₁ 2²/12²
I₂ = 1 2.78 10⁻²
I₂ = 2.78 10⁻² W / m²
b) r = 21 m
I₃ = I₁ r₁² / r₃²
I₃ = 1 2²/21²
I₃ = 9 10⁻² W/m²
c) in this case I₄ = I₀
I₁ r₁² = I₄ r₄²
R₄² = I₁ / I₄ r₁²
R₄² = 1 / 10⁻¹² 2²
R₄² = 4 10¹²
R₄ = 2 10⁶ m
<h2>Answer: medium </h2><h2 />
The propagation velocity of a wave depends on the medium in which it propagates.
In addition, it depends on the type of wave, for example a mechanical or electromagnetic wave.
In any case, the velocity of a wave is generally related to the value of the wavelength and the period, and can be expressed mathematically through the following formula:
where is the velocity of the wave, is the wavelength and is the period.
Therefore:
<h2>The propagation velocity of a wave depends on the <u>medium</u></h2>