A helium balloon ride lifts up passengers in a basket. Assume the density of air is 1.28 kg/m3 and the density of helium in the
1 answer:
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Explanation:
Using table A-3, we will obtain the properties of saturated water as follows.
Hence, pressure is given as p = 4 bar.
= 2553.6 kJ/kg
At state 2, we will obtain the properties. In a closed rigid container, the specific volume will remain constant.
Also, the specific volume saturated vapor at state 1 and 2 becomes equal. So,
According to the table A-4, properties of superheated water vapor will obtain the internal energy for state 2 at and temperature
so that it will fall in between range of pressure p = 5.0 bar and p = 7.0 bar.
Now, using interpolation we will find the internal energy as follows.
= 2963.2 - 2.005
= 2961.195 kJ/kg
Now, we will calculate the heat transfer in the system by applying the equation of energy balance as follows.
Q - W = ......... (1)
Since, the container is rigid so work will be equal to zero and the effects of both kinetic energy and potential energy can be ignored.
= 0
Now, equation will be as follows.
Q - W =
Q - 0 =
Q =
Now, we will obtain the heat transfer per unit mass as follows.
= (2961.195 - 2553.6)
= 407.595 kJ/kg
Thus, we can conclude that the heat transfer is 407.595 kJ/kg.
Answer:
The correct answer is option 'c': 30 AUs
Explanation:
For a spherical wave front emitted by sun with total energy 'E' the energy density over the surface when it is at a distance 'r' from the sun is given by
This energy per unit area is sensed by observer as intensity of the sun.
Let the initial intensity of sun at a distance be
Thus if the sun becomes 900 times dimmer we have
Thus the distance increases 30 times.