KVPY Government Jobs Exams

Jet aircrafts fly at altitudes above 30,000 ft where the air is very cold at – 40ºC and the pressure is 0.28 atm.
The cabin is maintained at 1 atm pressure by means of a compressor which exchanges air from outside
adiabatically. In order to have a comfortable cabin temperature of 25ºC, we will require in addition -
(A) a heater to warm the air injected into the cabin
(B) an air-conditioner to cool the air injected into the cabin
(C) neither a heater nor an air-conditioner ; the compressor is sufficient
(D) alternatively heating and cooling in the two halves of the compressor cycle

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KVPY Other Question
A container with rigid walls is covered with perfectly insulating material. The container is divided into two
parts by a partition. One part contains a gas while the other is fully evacuated (vacuum). The partition is
suddenly removed. The gas rushes to fill the entire volume and comes to equilibrium after a little time. If the
gas is not ideal,
(A) the initial internal energy of the gas equals its final internal energy
(B) the initial temperature of the gas equals its final temperature
(C) the initial pressure of the gas equals its final pressure
(D) the initial entropy of the gas equals its final entropy A speaker emits a sound wave of frequency f0. When it moves towards a stationary observer with speed u,
the observer measures a frequency f1. If the speaker is stationary, and the observer moves towards it with
speed u, the measured frequency is f2. Then -
(A) f1 = f2 < f0 (B) f1 > f2 (C) f1 < f2 (D) f1 = f2 > f0