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MCQEasyJEE 2023Newton's First Law

JEE Physics 2023 Question with Solution

Given below are two statements: one is labelled as Assertion A and the other one is labelled as Reason R.

Assertion A: An electric fan continues to rotate for some time after the current is switched off.

Reason R: Fan continues to rotate due to inertia of motion.

In the light of the above statements, choose the most appropriate answer from the options given below.

  • A

    A is not correct but R is correct

  • B

    Both A and R are correct and R is the correct explanation of A

  • C

    Both A and R are correct but R is NOT the correct explanation of A

  • D

    A is correct but R is not correct

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: Assertion A states that an electric fan continues to rotate for some time after the current is switched off. Reason R states that the fan continues to rotate due to inertia of motion.

Find: The correct option among the given Assertion-Reason choices.

From the solution text, Assertion A is correct because the fan does not stop immediately when current is switched off. The rotating blades continue moving for some time.

Reason R is also correct because inertia of motion makes a moving object tend to continue in its state of motion unless an external retarding effect brings it to rest.

Therefore, both Assertion A and Reason R are correct, and Reason R correctly explains Assertion A.

However, the solution labels the correct option as A, while its written explanation matches the second listed option. Hence, the correct answer corresponding to the option text is B.

Answer Discrepancy Note

Given: The option list shows the statement "Both A and R are correct and R is the correct explanation of A" as option B.

Find: Which answer should be recorded.

The worked explanation explicitly concludes:

  1. Assertion A is correct.
  2. Reason R is correct.
  3. Reason R correctly explains Assertion A.

This conclusion matches option B in the provided options.

So, even though the solution says "The Correct Option is A", the actual explanation supports B. Therefore, the defensible final answer is B.

Common mistakes

  • Confusing inertia of motion with continued supply of current. The fan does not keep rotating because current is still flowing; it rotates briefly because the blades already have motion. Focus on the physical principle after switch-off.

  • Reading only the solution and ignoring the explanation. Here the header says option A, but the written reasoning matches option B. Always verify which option text the explanation supports.

  • Assuming that if both Assertion and Reason are true, the answer must always be the "both true" option. You must also check whether the Reason actually explains the Assertion, not merely whether it is true.

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