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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Circular Motion

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Circular Motion

A rod of length L is pivoted at one of its ends and rotated in a...

A rod of length LL is pivoted at one of its ends and rotated in a horizontal plane with a uniform angular velocity. Let T1T_1 and T2T_2 represent the tensions at distances L/4L/4 and 3L/43L/4, respectively, from the pivoted end.

Options

  1. AThe relationship between T1T_1 and T2T_2 depends on whether the rotation is clockwise or anticlockwise
  2. BT1=T2T_1 = T_2
  3. CT2>T1T_2 > T_1
  4. DT1>T2T_1 > T_2

Correct answer

D. T1>T2T_1 > T_2

Step-by-step solution

Let the mass per unit length of the rod be λ\lambda and its angular velocity be ω\omega.

Consider an element of length dxdx at a distance xx from the pivoted end. The centripetal force required for this element is dF=(λdx)ω2xdF = (\lambda dx) \omega^2 x.

The tension T(x)T(x) at a distance xx from the pivot provides the necessary centripetal force for the remaining portion of the rod from xx to LL.

T(x)=∫xLλω2x′dx′=λω22(L2−x2)T(x) = \int_x^{L} \lambda \omega^2 x' dx' = \dfrac{\lambda \omega^2}{2} (L^2 - x^2)

Since T(x)T(x) is a decreasing function of xx, the tension is greater at points closer to the pivot.

Given x1=L4x_1 = \dfrac{L}{4} and x2=3L4x_2 = \dfrac{3L}{4}, we have x1<x2x_1 < x_2.

Therefore, T1>T2T_1 > T_2.
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