System of Particles and Rotational Motion Class 11 Physics Notes – Formulas & Quick Revision

Rotational Motion Class 11 ka sabse challenging chapter mana jata hai — centre of mass, torque, angular momentum aur moment of inertia yahan cover hote hain. Yahan aapko is chapter ke sabse important formulas aur quick revision points free milte hain — NCERT/CBSE syllabus ke hisaab se, boards aur JEE/NEET dono ke liye.

Important Formulas & Concepts — System of Particles and Rotational Motion

• Centre of mass: x_cm = Σmᵢxᵢ/Σmᵢ
• Torque τ = r × F = Iα
• Angular momentum L = Iω = mvr; dL/dt = τ
• Conservation: I₁ω₁ = I₂ω₂ (jab τ_ext = 0)
• MOI: ring MR², disc ½MR², solid sphere (2/5)MR², rod ML²/12
• Parallel axis theorem: I = I_cm + Md²
• Perpendicular axis theorem: I_z = I_x + I_y (planar bodies)
• Rolling on incline: a = g·sinθ/(1 + k²/R²)

Quick Revision Points

• Translational ↔ rotational analogy yaad rakho (F↔τ, m↔I, v↔ω, p↔L)
• Ice-skater haath sikodti hai to ω badh jata hai (L conserved)
• Rolling without slipping: v = Rω
• Sphere incline par pehle pahunchta hai (lowest k²/R²)
• MOI table rat lo — direct questions aate hain

FAQ

Moment of inertia yaad karne ka easy tarika?

Complete PDF mein visual MOI chart hai — shapes ke saath colour-coded, ratta nahi lagana padega.

NEET ke liye kitna important?

Rotational se 1-2 questions pakke hain NEET Physics mein.

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