Consider a fuel cell operating at 800∘C, 1 atm. In the cathode, humidified air is supplied with the mole fraction of water vapor
equal to 0.1. If the fuel cell employs circular flow channels with a diameter of 1 mm, find the maximum velocity of air that can be used while still maintaining laminar flow. Compare your result to Example 5.2.
1 answer:
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Answer: 6,400 km
Explanation:
The weight of a person is given by:
where m is the mass of the person and g is the acceleration due to gravity. While the mass does not depend on the height above the surface, the value of g does, following the formula:
where
G is the gravitational constant
M is the Earth's mass
r is the distance of the person from the Earth's center
The problem says that the person weighs 800 N at the Earth's surface, so when r=R (Earth's radius):
(1)
Now we want to find the height h above the surface at which the weight of the man is 200 N:
(2)
If we divide eq.(1) by eq.(2), we get
By solving the equation, we find:
which has two solutions:
--> negative solution, we can ignore it
--> this is our solution
Since the Earth's radius is , the person should be at
above Earth's surface.
Answer:
250 m/min down the road
Explanation:
Velocity is equivalent to speed but it considers the direction of the object. Velocity is also calculated by dividing the distance travelled by time. Therefore, where d and t are distance and time respectively. Given that d is given as 350 m and t is 1.4 s then by substitution
and the direction is down the road.
Velocity is 250 m/min down the road