Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEET
Exam
NEET
Subject
Physics
Chapter
Rotational Motion

NEET · Physics · Rotational Motion

A thin uniform rod, pivoted at O , is rotating in the horizontal...

A thin uniform rod, pivoted at OO, is rotating in the horizontal plane with constant angular speed ω\omega, as shown in the figure. At time t=0t=0, a small insect starts from OO and moves with constant speed vv, with respect to the rod towards the other end. It reaches the end of the rod at t=Tt=T and stops. The angular speed of the system remains ω\omega throughout. The magnitude of the torque (∣τ⃗∣)(|\vec{\tau}|) about OO, as a function of time is best represented by which plot? A thin uniform rod, pivoted at O , is rotating in the horizontal plane with constant angular speed ω , as shown in the

Options

  1. AWhich among the following elements have lowest value of IE _ 1 ?
  2. BWhich among the following elements have lowest value of IE _ 1 ?
  3. CWhich among the following elements have lowest value of IE _ 1 ?
  4. DWhich among the following elements have lowest value of IE _ 1 ?

Correct answer

B. Which among the following elements have lowest value of IE _ 1 ?

Step-by-step solution

Angular momentum, ∣L∣|\mathbf{L}| or L=IωL=I \omega (about axis of rod) Moment of inertia of the rod-insect system. I=Irod +mx2=Irod +mv2t2I=I_{\text{rod }}+m x^{2}=I_{\text{rod }}+m v^{2} t^{2} Here, m=m= mass of insect ∴L=(Irod+mv2t2)ω\therefore \quad L=\left(I_{\mathrm{rod}}+m v^{2} t^{2}\right) \omega Now ∣τ∣=dLdt=(2mv2tω)|\tau|=\frac{d L}{d t}=\left(2 m v^{2} t \omega\right) or ∣τ∣∝t|\tau| \propto t i.e. the graph is straight line passing through origin. After time T,L=T, L= constant ∴∣τ∣ or dLdt=0\therefore \quad|\tau| \text{ or } \frac{d L}{d t}=0 i.e., when the insect stops moving, LL does not change and therefore TT becomes constant.
Practice Rotational Motion on Quantrex Academy →

More from Rotational Motion

A solid sphere A of radius R and mass M is attached at a point to a smaller solid sphere… NEET 2026The angular speed of a flywheel is increased from 600 rpm to 1200 rpm in 10 s. The number… NEET 2026A thin wire of length ' L ' and linear mass density ' m ' is bent into a circular ring… NEET 2026A thin horizontal disc is rotating about a vertical axis passing through its fixed centre… NEET 2026The Sun rotates around its centre once in 27 days. What will be the period of revolution… NEET 2025A sphere of radius R is cut from a larger solid sphere of radius 2 R as shown in the… NEET 2025The radius of gyration of a solid sphere of mass 5 kg about X Y is 5 m as shown in… NEET 2024A wheel of a bullock cart is rolling on a level road as shown in the figure below. If its… NEET 2024 Full Rotational Motion list All NEET PYQs