Assertion (A) & Reason (B) MCQ

MCQ 11 Mark

Assertion: When a glass of hot milk is placed in a room and allowed to cool, its entropy decreases.
Reason: Allowing hot object to cool does not violate the second law of thermodynamics.

A
Assertion and reason both are correct statements and reason is correct explanation for assertion.
B
Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C
Assertion is correct statement but reason is wrong statement.
D
Assertion is wrong statement but reason is correct statement.

Answer

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
Explanation: Assertion and reason both are correct statements but reason is not correct explanation for assertion.

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MCQ 21 Mark

Assertion (A): Generally the path of a projectile from the earth is parabolic but it is elliptical for projectiles going to a very large height.
Reason (R): The path of a projectile is independent of the gravitational force of earth.

A
Both A and R are true and R is the correct explanation of A.
B
Both A and R are true but R is not the correct explanation of A.
C
A is true but R is false.
D
A is false but R is true.

Answer

(c) A is true but R is false.
Explanation: Upto ordinary heights, the change in the distance of a projectile from the centre of earth is negligible compared to the radius of earth. Hence the projectile moves under a nearly uniform gravitational force and the path is parabolic. But for the projectiles moving to a large height the gravitational force decreases quite rapidly (as $F \propto \frac{1}{r^2}$ ). Under such a rapidly decreasing variable force, the path of the projectile becomes elliptical.

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MCQ 31 Mark

Assertion: Two particles moving in the same direction do not lose all their energy in a completely inelastic collision.
Reason: Principle of conservation of momenturm holds true for all kinds of collisions.

A
Assertion and reason both are correct statements and reason is correct explanation for assertion.
B
Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C
Assertion is correct statement but reason is wrong statement.
D
Assertion is wrong statement but reason is correct statement.

Answer

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
Explanation: If it is a completely inelastic collision then:
$
\begin{aligned}
& m_1 v_1+m_2 v_2=m_1 v+m_2 v \\
& \text { or } v=\frac{m_1 v_1+m_2 v_2}{m_1+m_2} \\
& KE=\frac{p_1^2}{2 m_1}+\frac{p_2^2}{2 m_2}
\end{aligned}
$
As $\vec{P}_1$ and $\vec{P}_2$ both simultaneously cannot be zero, therefore total KE cannot be lost.

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MCQ 41 Mark

Assertion: A person feels weightlessness in an artificial satellite of the earth. However a person on the moon (natural satellite) feels his weight.
Reason: Satellite (natural or artificial) of a planet is a freely falling body.

A
Assertion and reason both are correct statements and reason is correct explanation for assertion.
B
Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C
Assertion is correct statement but reason is wrong statement.
D
Assertion is wrong statement but reason is correct statement.

Answer

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Physics Assertion (A) & Reason (B) MCQ

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