JEE Main 2026 · 2 Apr · Shift 2 · Physics Q50

← JEE Main 2026 · 2 Apr · Shift 2

PhysicsInteger+4 / -1Question 50 of 75

Moment of inertia about an axis $AB$ for a rod of mass 40 kg and length 3 m is same as that of a solid sphere of mass of 10 kg and radius $R$ about an axis parallel to $AB$ axis with separation of 3 m as shown in figure below. The value of $R$ is given as $\sqrt{\dfrac\alpha2}$ . The value of $\alpha$ is ________.

A vertical axis AB. A horizontal rod of length 3 m and mass M = 40 kg has its right end on AB. Below it, a solid sphere of radius R rotates about its own vertical axis (dotted line through its centre, with a curved arrow), which is parallel to AB at a distance of 3 m.

Your answer

Answer and worked solution

Official answer: 60

Rod about AB (axis through one end, perpendicular to the rod): $I=\frac{ML^2}3=\frac{40\times9}3=120$ kg m².

Sphere. The figure shows the sphere spinning about its own axis (the dotted line through its centre), which is parallel to AB and 3 m from it. About that axis $I=\frac25mR^2=4R^2$ .

Equate. $4R^2=120$ gives $R^2=30=\frac{60}2$ , so $\alpha=60$ .

Answer: 60

Topics:Moment of inertia Parallel and perpendicular axis theorems

← Previous question Next question →

JEE Main 2026 · 2 Apr · Shift 2, Physics question 50