System of Particles and Rotational Motion Class 11 Physics
In this chapter, you will learn about System of Particles and Rotational Motion in Class 11 Physics, an important topic for your board exams, JEE, and NEET preparation. Master the concepts with our free resources below.
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Chapter Notes
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Download System of Particles and Rotational Motion Notes PDFKey Concepts
- Centre of mass and its motion: Centre of mass and its motion
- Angular velocity, angular acceleration: Angular velocity, angular acceleration
- Torque and moment of inertia: Torque and moment of inertia
- Conservation of angular momentum: Conservation of angular momentum
- Rolling motion (pure rolling): Rolling motion (pure rolling)
Important Formulas
Torque:
τ = Iα
Angular momentum:
L = Iω
Kinetic energy (rolling):
KE = ½mv² + ½Iω²
Parallel axis theorem:
I = I_cm + md²
Solved Numerical Examples
Example 1
Problem: A solid cylinder of mass 2 kg and radius 0.5 m is rotating about its axis with an angular speed of 10 rad/s. Find its kinetic energy.
Solution: Moment of inertia for a solid cylinder I = ½MR² = ½ × 2 × (0.5)² = 0.25 kg·m². Kinetic energy K = ½Iω² = ½ × 0.25 × (10)² = ½ × 25 = 12.5 J.
Example 2
Problem: Calculate the torque required to produce an angular acceleration of 5 rad/s² in a body having a moment of inertia of 3 kg·m².
Solution: Torque τ = Iα. Here I = 3 kg·m² and α = 5 rad/s². τ = 3 × 5 = 15 N·m.
Daily Practice Problems (DPP)
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Previous Year Questions (PYQs)
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Common Mistakes
- Forgetting to convert units appropriately.
- Misapplying the sign convention.
- Ignoring vector components in calculations.