Q69 / 75 · JEE Main 2025 (29 Jan Shift 1) · Physics

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Time period of a simple pendulum is longer at the top of a mountain than that at the base of the mountain. Reason (R): Time period of a simple pendulum decreases with increasing value of acceleration due to gravity and vice-versa. In the light of the above statements, choose the most appropriate answer from the options given below :

  • Correct answer
    A
    Both \((\mathbf{A})\) and \((\mathbf{R})\) are true and \((\mathbf{R})\) is the correct explanation of \((\mathbf{A})\)
  • B
    (A) is true but (R) is false
  • C
    (A) is false but (R) is true
  • D
    Both \((\mathbf{A})\) and \((\mathbf{R})\) are true but \((\mathbf{R})\) is not the correct explanation of \((\mathbf{A})\)

Solution

As h increases, g decreases, T increases $\begin{aligned} & \mathrm{T}=2 \pi \sqrt{\frac{\ell}{\mathrm{~g}}} \\ & \mathrm{~g}=\frac{\mathrm{g}_0 \mathrm{R}^2}{(\mathrm{R}+\mathrm{h})^2} \end{aligned}$

Hence, the correct answer is option: 'A'.

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