Question

Assertion :The apparent weight of a body in an elevator moving with some downward acceleration is less than the actual weight of a body. Reason: The part of the weight is spent on producing downward acceleration, when body is in elevator.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

Let the mass of the body be $m$

$\therefore$ Actual weight of the body in an elevator at rest, $W=mg$

Now let the elevator moves downward with an acceleration $a$

Using Newton's law of motion: $ma=mg-N$ ........(1)

Thus it seems that a part of weight is spent to produce the downward acceleration. Hence the reason statement is correct.

Equation (1) $⟹$ $N=mg-ma$

Thus, apparent weight of the body is less than the actual weight of the body.

Hence, the assertion statement is correct but reason is not the correct explanation of the assertion.