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Physics Assertion (A) & Reason (B) MCQ

Model Paper 2 · Rajasthan Board (RBSE) STD 11 Science (Rajasthan - English Medium). 4 questions.

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Assertion (A) & Reason (B) MCQ

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4 questions · timed · auto-graded

MCQ 11 Mark
Assertion (A): A planet moves faster, when it is closer to the sun in its orbit and vice versa.
Reason (R): Orbital velocity in orbital of planet is constant.
  • 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: According to Kepler's law of planetary motion, a planet revolves around the sun in such a way that its areal velocity is constant. i.e. it move faster, when it is closer the sun and vice-versa.
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MCQ 21 Mark
Assertion: When percentage errors in the measurement of mass and velocity are $1 \%$ and $2 \%$ respectively, the percentage error in KE is $5 \%$.
Reason: $\frac{\Delta E}{E}=\frac{\Delta m}{m}+\frac{2 \Delta v}{v}$
  • 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
Assertion and reason both are correct statements and reason is correct explanation for assertion.
Explanation: Kinetic energy, $E =\frac{1}{2} m v^2$
Differentiating both sides,
$
\begin{aligned}
& \frac{\Delta E}{E}=\frac{\Delta m}{m}+\frac{2 \Delta v}{v} \\
& \frac{\Delta E}{E}=\frac{1}{100}+2 \times \frac{2}{100}=\frac{5}{100}=5 \%
\end{aligned}
$
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MCQ 31 Mark
Assertion (A): If $\vec{A} \cdot \vec{B}=\vec{B} \cdot \vec{C}$, then $\vec{A}$ may not always be equal to $\vec{C}$.
Reason (R): The dot product of two vectors involves cosine of the angle between the two vectors.
  • 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
Both $A$ and $R$ are true and $R$ is the correct explanation of $A$.
Explanation: As $\vec{A} \cdot \vec{B}=\vec{B} \cdot \vec{C} \Rightarrow AB \cos \theta_1= BC \cos \theta_2$
$\Rightarrow A = C$, only when $\theta_1=\theta_2$
so when angle between $\vec{A}$ and $\vec{B}$ is equal to angle between $\vec{B}$ and $\vec{C}$, only then $\vec{A}$ equal to $\vec{C}$.
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MCQ 41 Mark
Assertion (A): State variables are required to specify the equilibrium state of the system.
Reason (R): Pressure is an intensive state variable.
  • 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
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Assertion (A) & Reason (B) MCQ - Physics STD 11 Science Questions - Vidyadip