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Question #42353
The Question
A system consists of a heavy base of mass resting on the horizontal floor of an elevator. A motor rigidly attached to the base drives a massless rod of length with a point mass at its free end. The rod rotates in a vertical plane with a constant angular velocity . The elevator accelerates upwards with a constant acceleration . Assume . What is the maximum internal torque the motor must provide to maintain the constant angular velocity, and what is the minimum mass of the base required so that it never loses contact with the elevator floor?
Options
- A.
- B.
- C.
- D.
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
Center of Mass (COM) Frame|Apparent Weight in Accelerating Elevators|Vector Cross-Products
Why This Question Is Tricky
Common Mistakes
This question tests the ability to analyze a multi-particle system with internal moving parts inside a non-inertial reference frame.
The primary trap lies in calculating the normal force for the lift-off condition.
Students often incorrectly equate the normal force to just the weight of the base minus the centrifugal force (), forgetting that the mass also contributes to the static weight of the system .
This specific omission leads directly to the distractor kg.
Additionally, failing to adjust the gravity vector to for the internal torque calculation traps students into choosing .
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | System of Particles and Rotational Motion - Class 11 Part 1 |
| Concept | Center of Mass (COM) Frame |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |