JEE Mains · Physics · STD 11 - System of particles and rotational motion
- JEE Mains 2021
- Medium
- MCQ
The figure shows two solid discs with radius \({R}\) and \({r}\) respectively. If mass per unit area is same for both, what is the ratio of \({MI}\) of bigger disc around axis \({AB}\) (Which is \(\perp\) to the plane of the disc and passing through its centre) of MI of smaller disc around one of its diameters lying on its plane? Given \('M'\) is the mass of the larger disc. (\(MI\) stands for moment of inertia)
Pick an option to check your answer.
Answer & Solution
Correct Answer
(C) \(2 {R}^{4}: {r}^{4}\)
Step-by-step Solution
Detailed explanation
Ratio of moment of inertia \(=\frac{\frac{1}{2} MR ^{2}}{\frac{1}{4} mr ^{2}}\)
\(=\frac{2 \sigma \pi R^{2} R^{2}}{\sigma \pi r^{2} r^{2}}=\frac{2 R^{4}}{r^{4}}\)
More questions from Physics
- A thin solid disk of 1 kg is rotating along its diameter axis at the speed of 1800 rpm. By applying an external torque of \(25 \pi \mathrm{Nm}\) for 40 s, the speed increases to 2100 rpm. The diameter of the disk is ________ m.JEE Mains 2025 Medium
- The three charges \(q / 2, q\) and \(q / 2\) are placed at the corners \(A , B\) and \(C\) of a square of side ' \(a\) ' as shown in figure. The magnitude of electric field \((E)\) at the comer \(D\) of the square, is
JEE Mains 2022 Medium - In a coil, the current changes form \(-2 \mathrm{~A}\) to \(+2 \mathrm{~A}\) in \(0.2 \mathrm{~s}\) and induces an emf of \(0.1 \mathrm{~V}\). The selfinductance of the coil is _______.JEE Mains 2024 Hard
- A sample contains mixture of helium and oxygen gas. The ratio of root mean square speed of helium and oxygen in the sample is _______.JEE Mains 2024 Hard
- A paramagnetic substance in the form of a cube with sides \(1\, cm\) has a magnetic dipole moment of \(20 \times 10^{-6}\, J/T\) when a magnetic intensity of \(60 \times 10^3\, A/m\) is applied. Its magnetic susceptibility isJEE Mains 2019 Medium
- An electron is constrained to move along the \(y-\)axis with a speed of \(0.1\, c\) (c is the speed of light) in the presence of electromagnetic wave, whose electric field is \(\overrightarrow{ E }=30 \hat{ j } \sin \left(1.5 \times 10^{7} t -5 \times 10^{-2} x \right)\, V / m\) The maximum magnetic force experienced by the electron will be: (given \(c=3 \times 10^{8}\, ms ^{-1}\) and electron charge \(\left.=1.6 \times 10^{-19} C \right)\)JEE Mains 2020 Medium
More PYQs from JEE Mains
- Two particles \(A\) and \(B\) of equal masses are suspended from two massless springs of spring constants \(K _{1}\) and \(K _{2}\) respectively.If the maximum velocities during oscillations are equal, the ratio of the amplitude of \(A\) and \(B\) isJEE Mains 2021 Medium
-
In the given circuit the sliding contact is pulled outwards such that electric current in the circuit changes at the rate of \(8 \mathrm{~A} / \mathrm{s}\). At an instant when R is \(12 \Omega\), the value of the current in the circuit will be ______ A.JEE Mains 2025 Medium