1
JEE Main 2021 (Online) 25th February Morning Shift
+4
-1
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : When a rod lying freely is heated, no thermal stress is developed in it.

Reason R : On heating, the length of the rod increases.

In the light of the above statements, choose the correct answer from the options given below :
A
A is true but R is false
B
A is false but R is true
C
Both A and B are true but R is NOT the correct explanation of A
D
Both A and R are true and R is the correct explanation of A
2
JEE Main 2021 (Online) 25th February Morning Shift
+4
-1
A diatomic gas, having $${C_p} = {7 \over 2}R$$ and $${C_v} = {5 \over 2}R$$, is heated at constant pressure. The ratio dU : dQ : dW :
A
5 : 7 : 3
B
3 : 7 : 2
C
5 : 7 : 2
D
3 : 5 : 2
3
JEE Main 2021 (Online) 24th February Evening Shift
+4
-1
If one mole of an ideal gas at (P1, V1) is allowed to expand reversibly and isothermally (A to B) its pressure is reduced to one-half of the original pressure (see figure). This is followed by a constant volume cooling till its pressure is reduced to one-fourth of the initial value (B $$\to$$ C). Then it is restored to its initial state by a reversible adiabatic compression (C to A). The net workdone by the gas is equal to :

A
$$- {{RT} \over {2(\gamma - 1)}}$$
B
$$RT\left( {\ln 2 - {1 \over {2(\gamma - 1)}}} \right)$$
C
$$RT\ln 2$$
D
$$0$$
4
JEE Main 2021 (Online) 24th February Evening Shift
+4
-1
On the basis of kinetic theory of gases, the gas exerts pressure because its molecules :
A
continuously lose their energy till it reaches wall.
B
are attracted by the walls of container.
C
suffer change in momentum when impinge on the walls of container.
D
continuously stick to the walls of container.
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