Doubtify – JEE Ki Taiyaari, Simple Bhasha Mein

  ❓ Concept 🎬 Rotational Motion — COM of Bent Rod in 59 Sec Rod seedhi nahi hai… right angle pe bent hai? 👉 Samajh jao — COM ko todna padega! 🧠⚙️ Is type ke questions JEE mein frequently aate hain, aur solution hamesha break–combine method se hota hai 🔥 🖼️ Concept Image ✍️ Short Explanation Centre of mass shape se directly nahi milta — mass distribution se milta hai. Isliye bent rod dekhte hi: 👉 use parts mein tod do. 🔹 Step 1 — Golden Rule of COM (FOUNDATION 💯)** Centre of mass depends on: Mass distribution NOT directly on bending or fancy shape Uniform rod ⇒ Mass ∝ Length \text{Mass} \propto \text{Length} 📌 Density same ⇒ longer part = heavier part. 🔹 Step 2 — Bent Rod ⇒ Break Into Parts Right-angle bent rod ko hamesha: 👉 2 straight rods mein tod do Har part: Uniform Known length Known orientation (x-axis ya y-axis) Yahin se problem simple ho jaati hai 😎 🔹 Step 3 — COM of Each Straight Rod (MOST IMPORTANT 🔥)** Unifo...

  ❓ Question A uniform rod of total length 5L is bent at a right angle , such that one arm has length 2L and the other arm has length 3L . Find the position of the centre of mass of the system. 🖼️ Question Image ✍️ Short Solution This is a standard JEE Centre of Mass problem . No integration needed — treat each arm separately and use weighted average 🔥 🔹 Step 1 — Split the system into two rods Since the rod is uniform : Mass ∝ length Let: Rod 1: length = 2L , along x-axis Rod 2: length = 3L , along y-axis Assume: Total mass = M Mass per unit length = λ \lambda λ Then: Mass of rod 1 = 2 λ L 2\lambda L Mass of rod 2 = 3 λ L 3\lambda L 🔹 Step 2 — Locate centre of mass of each part For a uniform straight rod , COM lies at its midpoint. COM of rod 1 (along x-axis): ( x 1 , y 1 ) = ( L , 0 ) (x_1, y_1) = (L, 0) COM of rod 2 (along y-axis): ( x 2 , y 2 ) = ( 0 , 3 L 2 ) (x_2, y_2) = (0, \tfrac{3L}{2}) 🔹 Step 3 — Use Centre...