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Question #42410
The Question
A thin uniform ring of mass and radius is released from rest at a vertical height on a rough downward incline. It rolls without slipping until it reaches the lowest point of the track (height ). At the lowest point, the track smoothly transitions via a short frictionless circular fillet to a frictionless upward incline of angle with the horizontal. The upward incline ends abruptly at a vertical height above the lowest point, from where the ring becomes a projectile in the air. Neglecting air resistance, find the total time of flight of the ring from the moment it leaves the track until it hits the horizontal ground (which is at height ). Take .
Options
- A.
2 \text{ s}
- B.
- C.
- D.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Variable_Constraint
Develop pure symbolic logic skills by mastering algebraic constraints without relying on numerical data.
Concepts Behind This Question
Time of Flight Logic|Rolling on Inclines|Laws of Motion
Why This Question Is Tricky
Common Mistakes
This question tests the 'Friction Transition' and 'Energy Partition' traps in rigid body dynamics.
Students commonly assume that a rolling body will continue to roll without slipping on a new incline, incorrectly reducing its translational kinetic energy to account for a decreasing rotational kinetic energy.
However, on a frictionless surface, no torque exists to change the angular velocity.
The rotational kinetic energy becomes 'locked' and does not convert back into potential or translational energy.
Failing to recognize this leads to an overestimated launch velocity.
Additionally, treating the ring as a point mass ignores the energy partitioned into rotation entirely, leading to an even larger incorrect velocity.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Motion in a Plane - Class 11 Part 1 |
| Concept | Time of Flight Logic |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |