JEE Main 2026 · 4 Apr · Shift 2 · Physics Q35

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PhysicsSingle correct+4 / -1Question 35 of 75

A uniform disc of radius $R$ and mass $M$ is free to oscillate about the axis $A$ as shown in the figure. For small oscillations the time period is ________.
( $g$ is acceleration due to gravity)

A vertical disc of radius R and mass M hangs from a horizontal axis A that touches its top edge and lies in the plane of the disc (a tangent); a curved arrow around the axis shows the rotation.

2\pi\sqrt{\dfrac{5R}{4g}}

2\pi\sqrt{\dfrac{2R}{3g}}

2\pi\sqrt{\dfrac{3R}{2g}}

2\pi\sqrt{\dfrac{3R}{g}}

Answer and worked solution

Official answer: A

Moment of inertia. The axis is tangent to the disc in its plane: $I=\frac{MR^2}4+MR^2=\frac54MR^2$ .

Compound pendulum ( $d=R$ ):
$T=2\pi\sqrt{\frac I{MgR}}=2\pi\sqrt{\frac{5R}{4g}}.$

(A)

Topics:Simple and compound pendulum Parallel and perpendicular axis theorems

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JEE Main 2026 · 4 Apr · Shift 2, Physics question 35