Student Login

Home›Chapters›Rotational Motion PYQs›Angular Momentum & its Conservation›Question 50

MHT CET 2021 (22 Sep, Shift 2) · Angular Momentum & its Conservation

Angular Momentum & its Conservation question from MHT CET 2021 (22 Sep, Shift 2)

Q50MHT CET 2021 · 22 SEP · SHIFT 2Medium

Angular Momentum & its Conservation

A child is standing with folded hands at the centre of the platform rotating about its central axis. The kinetic energy of the system is ' $K$ '. The child now stretches his arms so that the moment of inertia of the system becomes double. The kinetic energy of the system now is

Show answer and solution

Answer: (a)

No external torque, so $L = I\omega$ stays constant.
$K = \frac{L^2}{2I}$ , so $K \propto \frac{1}{I}$ for constant $L$ .
$I' = 2I \Rightarrow K' = \frac{K}{2}$
So the answer is (a) $\frac{K}{2}$ .

Report a mistake

More questions on Angular Momentum & its Conservation

Two discs have moments of inertia I1 and I2 about their respective axes perpendicular to…JEE Main 2021 (27 Aug, Shift 2)
A thin circular ring of mass M and radius r is rotating about its axis with an angular…JEE Main 2021 (18 Mar, Shift 1)
A wheel is rotating freely with an angular speed ω on a shaft. The moment of inertia of…JEE Main 2020 (5 Sep, Shift 1)
Two uniform circular discs are rotating independently in the same direction around their…JEE Main 2020 (2 Sep, Shift 2)
A circular disc of mass M and radius R is rotating about its axis with angular speed ω₁…JEE Main 2020 (4 Sep, Shift 1)
A person of 80 kg mass is standing on the rim of a circular platform of mass 200 kg…JEE Main 2020 (3 Sep, Shift 1)
Consider a uniform rod of mass M = 4m and length pivoted about its centre. A mass m…JEE Main 2020 (8 Jan, Shift 1)
A thin rod of mass 0.9 kg and length 1 m is suspended, at rest, from one end so that it…JEE Main 2020 (5 Sep, Shift 2)