Pablo's engineering team has developed a new material that is strong enough to withstand major impacts, including bullets, witho
ut breaking or deforming. He plans to design a new type of motorcycle helmet using the material as its outside covering. A prototype of the helmet is shown below. Pablo knows that other types of motorcycle helmets have outside coverings that bend and deform slightly on impact. So if Pablo's new helmet is going to be as effective at protecting people's heads as existing helmets, he'll need to
A.
slightly reduce the total mass of the new helmet by reducing the amount of internal cushioning.
B.
maximize the total mass of the helmet by adding flexible steel to the outside covering.
C.
increase the amount of cushioning on the inside of the new helmet to help it absorb impacts.
D.
use a thicker outside covering than other helmets to help prevent deformation even further.
A.
slightly reduce the total mass of the new helmet by reducing the amount of internal cushioning.
B.
maximize the total mass of the helmet by adding flexible steel to the outside covering.
C.
increase the amount of cushioning on the inside of the new helmet to help it absorb impacts.
D.
use a thicker outside covering than other helmets to help prevent deformation even further.
1 answer:
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Answer:
The temperature of the steam during the heat rejection process is 42.5°C
Explanation:
Given the data in the question;
the maximum temperature T in the cycle is twice the minimum absolute temperature T
in the cycle
T = 0.5T
now, we find the efficiency of the Carnot cycle engine
η = 1 - T
/T
η = 1 - T
/0.5T
η = 0.5
the efficiency of the Carnot heat engine can be expressed as;
η = 1 - W
/Q
where W is net work done, Q
is is the heat supplied
we substitute
0.5 = 60 / Q
Q = 60 / 0.5
Q = 120 kJ
Now, we apply the first law of thermodynamics to the system
W = Q
- Q
60 = 120 - Q
Q = 60 kJ
now, the amount of heat rejection per kg of steam is;
q = Q
/m
we substitute
q = 60/0.025
q = 2400 kJ/kg
which means for 1 kilogram of conversion of saturated vapor to saturated liquid , it takes 2400 kJ/kg of heat ( enthalpy of vaporization)
q = h
= 2400 kJ/kg
now, at h = 2400 kJ/kg from saturated water tables;
T = 40 + ( 45 - 40 ) (
)
T = 40 + (5) × (0.5)
T = 40 + 2.5
T = 42.5°C
Therefore, The temperature of the steam during the heat rejection process is 42.5°C