Class 12 Physics Rotational Dynamics Notes and Important Questions
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Notes for Class 12 Rotational Dynamics (Physics) are shown above.
Practice
Important Questions
What is the difference between moment of inertia of a rod about an axis passing through its one end and through its centre perpendicular to its length?
ML²/3
ML²/4
ML²/6
ML²/12
Define radius of gyration.
Calculate the moment of inertia of a thin uniform rod about an axis passing through its centre and perpendicular to its length.
A physics teacher stands on a freely rotating platform. He holds a dumbbell in each hand of his outstretched arms while a student gives him a push until his angular velocity reaches 1.5 rad/s. When the freely spinning teacher pulls his hands in close to his body, his angular velocity increases to 5.0 rad/s. What is the ratio of his final kinetic energy to initial kinetic energy?
If the rotational kinetic energy of a body is E and moment of inertia is I, then angular momentum will be:
EI
√2EI
E/I
√IE
Define the moment of inertia.
A uniform rod of mass m and length L is rotating about an axis AB passing through its one end and perpendicular to the length. Calculate the moment of inertia of the rod about the axis AB.
A fly wheel of moment of inertia 0.32 kgm² is rotated steadily at 120 rad/sec by a 50 watt electric motor. Calculate:
i) The kinetic energy of the fly wheel.
ii) The frictional couple opposing the rotation.
When the torque acting upon a system is zero which of the following will be constant?
Force
Linear momentum
Angular momentum
Angular acceleration
A ballet dancer sometimes stretches and sometimes folds her arms during her performance, why? Justify.
Establish a relation between torque and moment of inertia for a rigid body.
Why do we prefer a wrench of longer arm over a wrench of shorter arm?
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Exam
Past Question Analysis
Historical exam-pattern data from past NEB question papers — not a prediction of future questions.
6
Question Items
5
Total Marks
5
Papers Appeared In
| Year | Question Items | Marks |
|---|---|---|
| 2083 | 2 | 1 |
| 2082 | 1 | 1 |
| 2081 | 1 | 1 |
| 2080 | 1 | 1 |
| 2078 | 1 | 1 |
Also appears in 4 model questions (not counted above — model sets aren't actual NEB exam history).
Rotational Dynamics explores the motion and behavior of objects rotating about an axis. It covers angular displacement, angular velocity, angular acceleration, torque and angular momentum, along with moment of inertia and radius of gyration. Students also study rotational kinetic energy, work and power in rotational motion, and the principle of conservation of angular momentum.
This page covers Rotational Dynamics, chapter 1 of 25 in the Class 12 Physics syllabus set by the National Examination Board (NEB). 17 important questions for this chapter are available, each with a full solution.
For numerical and derivation-based chapters like this one, working through past NEB questions is usually more useful than re-reading notes alone — try solving each important question above before checking the solution, then compare your working step by step.