Space is more hostile to the human body.
Answer:
A downward force of magnitude 5 N is exerted on the book by the force of ... Do the downward force in Part A (gravity) and the upward force in Part B ...
Answer:
Moving up one step from there, a camera with a single element lens has a convex lens. It may be a meniscus lens which is convex on one side and concave on the other, but it is thicker in the middle than the edges and functions like a convex lens. (The meniscus shape helps the lens focus light on a flat focal plane.)
Answer:
false
Explanation:
since it has seven valence electrons it means it's a non metal and non metals always gain electrons.
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