Rotation SBT QNO 143 | Centre of Mass | Rotational and Translational Equilibrium | JEE / NEET

Rotation SBT QNO 143 | Centre of Mass | Rotational and Translational Equilibrium | JEE / NEET

In this video, we solve Question 143 from the SBT (Selected Book of Tests) — a challenging rotation and equilibrium problem involving a rigid square platform supported by springs.

When a 6 cm wooden block is inserted under one vertex, we explore how the platform tilts and calculate the change in height of its center using principles of rotational and translational equilibrium.

We use concepts of:

Center of mass and geometry of the platform

Equilibrium of forces (ΣF = 0)

Rotational equilibrium (Στ = 0)

Small angle/height approximation

This question beautifully ties together mechanics, rotation, and elasticity, making it perfect for JEE Main, JEE Advanced, and Class 11/12 physics preparation.

👉 Watch till the end for clear explanation, free-body diagrams, and reasoning behind each step.

📘 Topic: Rotation & Equilibrium
📗 Book: SBT (Selected Book of Tests)
📘 Question No.: 143
📕 Chapter: Rigid Body Dynamics / Rotational Motion

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