Which of the following are fire prevention guidelines?
2 answers:
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Answer:
The jet stream speed used by the computer is 142. km/h
Explanation:
The given parameters are;
The distance between the two cities the plane flies = 4,000 km
The difference in flight times for outgoing and return flights = 70.0 min
We note that 70 min = 70 min × 1 h/60 min = 7/6 h
The airspeed recommended by the airline computer = 1,000 km/h
Let 'a' represent the jet stream speed
The time it takes the plane moving in the same direction as the jet stream between the two cities, 't₁', is given as follows;
The time it takes the plane moving in the opposite direction as the jet stream between the two cities, 't₂', is given as follows;
The difference in flight times for outgoing and return flights, Δt = t₂ - t₁
Therefore, we have;
From which we get;
By cross multiplying, we have;
-48,000·a = 7·a²- 7,000,000
∴ 7·a² + 48,000·a - 7,000,000 = 0
Factorizing with a graphic calculator gives;
(7·a - 1,000)·(a + 7,000) = 0
∴ a = 1,000/7, or a = -7000
Therefore, the jet stream speed the computer is using, a = 1,000/7 km/h = 142. km/h.
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