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Question #42249
The Question
A gyroscope consists of a uniform solid disk of mass and radius mounted on a massless axle. The axle is attached to a frictionless pivot on the vertical axis of a rotating platform. The distance from the pivot to the center of mass of the disk is . The platform rotates at a constant angular velocity about the vertical axis. The gyroscope axle is observed to maintain a steady angle with the upward vertical, precessing together with the platform. Calculate the required spin angular velocity of the disk about its axle. (Take )
Options
- A.
77.5 \text{ rad/s}
- B.
40.0 \text{ rad/s}
- C.
75.0 \text{ rad/s}
- D.
2.5 \text{ rad/s}
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Intuition_Breaker
Train your brain to resist "obvious" answers that are designed to deceive your intuition.
Concepts Behind This Question
Frame of Reference Dependency|Gyroscopic Stability|Vector Cross-Products
Why This Question Is Tricky
Common Mistakes
This question exposes the 'Lethal Collision' of blindly applying the standard simplified gyroscopic precession formula () in a non-inertial setup.
Students often ignore the vector addition of the platform's angular velocity to the gyroscope's spin, which alters the total angular momentum vector.
Consequently, they miss the terms that arise from the cross product (physically manifesting as centrifugal torque and Coriolis effects on the extended rigid body).
Failing to account for the transverse moment of inertia and these fictitious torques leads directly to the trap answer of .
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | System of Particles and Rotational Motion - Class 11 Part 1 |
| Concept | Gyroscopic Stability |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |