KEAM 2021 Physics and Chemistry Solved Paper

Rotational kinetic energy is given as KR=‌

1

2

Iω2
where, I is moment of inertia and ω is angular frequency.
As, mass and radius of ring and disc is same.
So, I‌ring ‌=‌

1

2

MR2
and Idisc=‌

1

4

MR2
∴‌‌ The required ratio is,
‌

(KR)‌ring ‌

(KR)‌disc ‌

=‌

‌ 1 2 MR2

1 4 MR2

=‌

2

1