Verified Solution • 2025–26 Session moderate

QJEEM14Pheefd: JEE Main 2014 Physics - Class 11 JEEM14Pheefd Solution: A bob of mass attached to an inextensible string of length is…

A bob of mass mm attached to an inextensible string of length ll is suspended from a vertical support. The bob rotates in a horizontal circle with an angular speed ω rad/s\omega \,rad/s about the vertical. About the point of suspension:

Multiple Choice Options

  • A angular momentum is conserved
  • B angular momentum changes in magnitude but not in direction.
  • C angular momentum changes in direction but not in magnitude.
  • D angular momentum changes both in direction and magnitude.

Step-by-Step Verified Solution

JEE Main 2014 (Offline) Physics - Rotational Motion Question 202 English Explanation
Torque working on the bob of mass mm is, τ=mg×ℓ sin⁡ θ.\tau = mg \times \ell \,\sin \,\theta . (Direction of torque by the weight is parallel to plane of rotation of the particle)

As τ\tau is perpendicular to the angular momentum L→\overrightarrow L of the bob, so the direction of LL changes but magnitude remains same.

Related Learning Resources & Exam Preparation

JEE Main PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring