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Question #42410

Difficulty: 8/10 | 🟢 Free

The Question

A thin uniform ring of mass mm and radius RR is released from rest at a vertical height h=30 mh = 30 \text{ m} on a rough downward incline. It rolls without slipping until it reaches the lowest point of the track (height 00). At the lowest point, the track smoothly transitions via a short frictionless circular fillet to a frictionless upward incline of angle θ=30∘\theta = 30^\circ with the horizontal. The upward incline ends abruptly at a vertical height H=10 mH = 10 \text{ m} 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 00). Take g=10 m/s2g = 10 \text{ m/s}^2.

Options

  • A.

    2 \text{ s}

  • B.

    10+22 s\frac{\sqrt{10} + \sqrt{2}}{2} \text{ s}

  • C.

    1+3 s1 + \sqrt{3} \text{ s}

  • D.

    2 s\sqrt{2} \text{ s}

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

SubjectPhysics
ChapterMotion in a Plane - Class 11 Part 1
ConceptTime of Flight Logic
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree