Assertion (A) & Reason (B) MCQ

MCQ 11 Mark

Assertion (A): Horizontal range is same for the angle of projection $\theta$ and (90 - ).
Reason (R): Horizontal range is independent of angle of projection.

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: Horizontal range, $R _1=\frac{u^2 \sin 20}{g}$ for angle $\theta$
$
\begin{aligned}
& R_2=\frac{u^2 \sin 2\left(90^{\circ}-\theta\right)}{g}=\frac{u^2 \sin 2 \theta}{g} \text { for angle }\left(90^{\circ}-\theta\right) \\
& \therefore R_1=R_2
\end{aligned}
$
Hence horizontal range is same for angle of projection $\theta$ and $\left(90^{\circ}-\theta\right)$ and the horizontal range depends on the angle of projection.

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MCQ 21 Mark

Assertion (A): There is no effect of rotation of the earth on acceleration due to gravity at poles.
Reason (R): The rotation of the earth is about the polar axis.

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

(a) Both A and R are true and R is the correct explanation of A .
Explanation: At poles, the radius of the horizontal circle is zero.
$\therefore$ Centripetal force $F = mr \omega^2=0$.
Hence $g$ at poles is not affected by the rotation of the earth.

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MCQ 31 Mark

Assertion: It is not possible for a system, unaided by an external agency to transfer heat from a body at lower temperature to another body at a higher temperature.
Reason: According to Clausius statement “No process is possible whose sole result is the transfer of heat from a cooled object to a hotter object.”

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: Second law of thermodynamics can be explained with the help of example of refrigerator, as we know that refrigerator, the working substance extracts heat from colder body and rejects a large amount of heat to a hotter body with the help of an external agency, i. e, the electric supply of the refrigerator. No refrigerator can ever work without external supply of electric energy to it.

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MCQ 41 Mark

Assertion (A): Mass and energy are not conserved separately, but are conserved as a single entity called mass energy.
Reason (R): Mass and energy conservation can be obtained by Einstein equation for energy.

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

(a) Both A and R are true and R is the correct explanation of A .
Explanation: $\Rightarrow$ From Einstein equation $E = mc ^2$
it can be observed that if mass is conserved then only energy is conserved and vice versa. Thus, both cannot be treated separately.

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Physics Assertion (A) & Reason (B) MCQ

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