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Two simple pendulums having lengths l_1 and l_2 with negligible string mass undergo angular displacements theta_1 and theta_2, from their mean positions, respectively. If the angular accelerations of both pendulums are same, then which expression is correct?

Solution & Explanation

### Related Formula Angular acceleration definition for a simple pendulum swinging at small angle theta: alpha = -omega^2 theta where: omega = sqrtfracgl implies omega^2 = fracgl Hence, the magnitude of angular acceleration is: alpha = fracgltheta ### Core Logic Given that angular accelerations are exactly identical in magnitude (alpha_1 = alpha_2): fracgl_1theta_1 = fracgl_2theta_2 ### Step 1: Simplify Expression Cancelling out the constant gravitational field factor g: fractheta_1l_1 = fractheta_2l_2 implies theta_1 l_2 = theta_2 l_1 ### Pattern Recognition Angular acceleration scales inversely with length for a fixed angle. To preserve equal acceleration values, the product theta cdot l^-1 must be constant, resulting in cross-multiplication balance. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Physics: Oscillations

Reference Study Guides

More Oscillations Previous-Year Questions — Page 2

Q5 2025 Simple Pendulum
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. [cite: 1, 5] Reason (R) : Time period of a simple pendulum decreases with increasing value of acceleration due to gravity and vice-versa. [cite: 1, 5] In the light of the above statements, choose the most appropriate answer from the options given below:
  • A. textBoth (A) and (R) are true but (R) is not the correct explanation of (A).
  • B. textBoth (A) and (R) are true and (R) is the correct explanation of (A).
  • C. text(A) is true but (R) is false.
  • D. text(A) is false but (R) is true.

Solution

### Related Formula T = 2pisqrtfraclg ### Core Logic As altitude h increases at the top of a mountain, acceleration due to gravity g drops down according to [cite: 634, 635]: g = fracg_0 R^2(R+h)^2 Since T propto frac1sqrtg, a decreased g directly makes the time period T longer[cite: 634, 635]. ### Pattern Recognition Higher altitude implies smaller gravity field implies slower pendulum oscillations implies longer period[cite: 634, 635]. ### Chapter Mix Class 11 Physics: Oscillations Class 11 Physics: Gravitation

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