Rotational Motion – Phase 2 (Page 6)
IIT-JEE Tough Problems (Advanced Level)
These problems are concept-heavy and appear in IIT-JEE Advanced / Tough JEE Main sections. Focus on logic, not speed.
TP-1 (IIT-JEE Advanced)
A uniform rod of length L and mass M is free to rotate in a horizontal plane about one end. A particle of mass m strikes the free end perpendicular to the rod with velocity v and sticks to it. Find the angular velocity just after collision.
Solution:
No external torque about hinge ⇒ angular momentum conserved.
Initial angular momentum:
Li = m v L
Final moment of inertia:
I = ML²/3 + mL²
Using Li = Iω:
ω = (m v L) / (ML²/3 + mL²)
Answer: ω = m v / (L(M/3 + m))
TP-2 (IIT-JEE)
A disc of mass M and radius R is rotating freely with angular speed ω. A ring of same mass and radius is gently placed on it concentrically. Find final angular speed.
Solution:
No external torque ⇒ angular momentum conserved.
Initial: Li = (½MR²)ω
Final moment of inertia:
I = ½MR² + MR² = 3/2 MR²
ωf = (½MR² ω) / (3/2 MR²)
Answer: ωf = ω / 3
TP-3 (JEE Advanced)
A cylinder rolls down an incline of angle θ. Find the frictional force acting on it.
Solution:
Equations:
Mg sinθ − f = Ma
fR = Iα
For cylinder: I = ½MR², α = a/R
Solving:
a = (2/3) g sinθ
f = Mg sinθ − Ma
Answer: f = (1/3) Mg sinθ
TP-4 (IIT-JEE Advanced)
A flywheel of moment of inertia I rotates at ω. Energy stored is used to lift a mass m slowly. Find maximum height reached.
Solution:
Initial energy = rotational KE
½ Iω² = mgh
Answer: h = Iω² / (2mg)
TP-5 (IIT-JEE)
Two discs of same radius but different masses rotate with same angular speed. Which has greater angular momentum?
Logic:
Angular momentum L = Iω
Heavier disc → larger I → larger L
Answer: Heavier disc
HOW TO HANDLE TOUGH IIT PROBLEMS
✔ Identify conservation law first
✔ Choose axis carefully
✔ Do NOT rush into equations
✔ Write I clearly before substitution
✔ Trust physics, not memory
Next: Phase 2 – Page 7 (Even Tougher Multi-Concept Problems)
📘 IIT–JEE Physics Mega Library
Complete Intermediate + IIT/JEE Physics Preparation Hub
Concepts • Problems • Exam Mastery • Topper Thinking
🔄 Rotational Motion – Phase 3 (Exam Mastery Series)
Advanced exam-oriented thinking series focusing on traps, execution, pressure handling, and topper strategies.
- Phase 3 – Page 1
- Phase 3 – Page 2
- Phase 3 – Page 3
- Phase 3 – Page 4
- Phase 3 – Page 5
- Phase 3 – Page 6
- Phase 3 – Page 7
- Phase 3 – Page 8
- Phase 3 – Page 9
- Phase 3 – Page 10
- Phase 3 – Page 11
- Phase 3 – Page 12
- Phase 3 – Page 13
- Phase 3 – Page 14
- Phase 3 – Page 15
- Phase 3 – Page 16
- Phase 3 – Page 17
- Phase 3 – Page 18
- Phase 3 – Page 19
- Phase 3 – Page 21
- Phase 3 – Page 22
- Phase 3 – Page 23
- Phase 3 – Page 24
- Phase 3 – Page 25
- Phase 3 – Page 26
- Phase 3 – Page 27
- Phase 3 – Page 28
- Phase 3 – Page 29
- Phase 3 – Page 30
- Phase 3 – Page 31
- Phase 3 – Page 32
- Phase 3 – Page 33
- Phase 3 – Page 34
- Phase 3 – Page 35
- Phase 3 – Page 36
- Phase 3 – Page 37
- Phase 3 – Page 38
- Phase 3 – Page 39
📚 Complete Physics Libraries
- Momentum & Collisions – Complete Library
- Centre of Mass & System of Particles – Complete Library
- Work, Energy & Power – Complete Library
🧠 Advanced Thinking & Core Notes
- Physics Thinking Library – How IIT Toppers Think
- Intermediate Physics – IIT/JEE Complete Notes
- Units & Measurements – Complete Notes
🌐 Student Learning Channels
This library is designed to convert preparation into rank.
Study systematically • Think like a topper • Execute with confidence
No comments:
Post a Comment