Answer:
ºC
Explanation:
First, let's write the energy balance over the duct:

It says that the energy that goes out from the duct (which is in enthalpy of the mass flow) must be equals to the energy that enters in the same way plus the heat that is added to the air. Decompose the enthalpies to the mass flow and specific enthalpies:

The enthalpy change can be calculated as Cp multiplied by the difference of temperature because it is supposed that the pressure drop is not significant.

So, let's isolate
:

The Cp of the air at 27ºC is 1007
(Taken from Keenan, Chao, Keyes, “Gas Tables”, Wiley, 1985.); and the only two unknown are
and Q.
Q can be found knowing that the heat flux is 600W/m2, which is a rate of heat to transfer area; so if we know the transfer area, we could know the heat added.
The heat transfer area is the inner surface area of the duct, which can be found as the perimeter of the cross section multiplied by the length of the duct:
Perimeter:

Surface area:

Then, the heat Q is:

Finally, find the exit temperature:

=27.0000077 ºC
The temperature change so little because:
- The mass flow is so big compared to the heat flux.
- The transfer area is so little, a bigger length would be required.
Answer:
Proof is given below
Explanation:
The length contraction is given by Δx = Δx' *√(1 - v² / c²)
where Δx' is the proper length and is measured in the frame where the object is at rest
Since the y' and z' axes are perpendicular to the direction of motion there is no contraction
So if you let V0 = Δy' * Δz' *Δx'
and V = Δy * Δz * Δx = Δy'* Δz' * Δx
Then
V = V0 * √(1 - v² / c²)
Answer: The lithosphere and the asthenosphere
B. Energy enters and exits the system matter does not
Explanation:
In thermodynamics, there are three types of system:
- Open system: it is a system that exchanges both matter and energy with the surroundings - an example is an open bottle
- Closed system: it is a system that exchanges only matter with the surroundings, while energy cannot enter and exit the system - an example is a closed bottle (air cannot enter/exit the bottle, but heat can be exchanged through the walls of the bottle)
- Isolated system: it is a system that cannot exchange matter or energy with the surroundings - an example is a sealed thermic container (heat cannot pass through the walls)
In this problem, we are asked to identify which statement best describes the island food web as a closed system: based on the definitions above, we can say that the correct option is
B. Energy enters and exits the system matter does not
Learn more about thermodynamics:
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