Mechanics Problem Solving - NLM & Friction - 4 | Class 11, NEET, IIT JEE | Rohit Ranjan (IIT KGP)

Описание: In this video (Part 4 of the Mechanics Problem-Solving Series), we explore two important examples based on constraints in pulley–string systems.
These problems help students understand how the motion of one part of a system automatically restricts the motion of the others.

We solve two advanced but essential constraint-based examples:
✅ Example 1: Two tensions + constraint relation

A string is attached to the ceiling, passes over a pulley, one end goes to a block on a horizontal surface, and a mass is hanging on the pulley.
You will learn:

How to find tension in both strings

How to write the constraint equation

How the movement of one block affects the other

How to calculate accelerations of both bodies

FBDs for constraint relations, multi-body systems

This example builds the foundation for all complex JEE/NEET pulley questions.

✅ Example 2: Ends P and Q moving downward with speed U

An unstretchable string has ends P and Q both moving downward with uniform speed U.
Two pulleys A and B are fixed.
A block of mass M is attached, making an angle θ with the fixed pulleys.

You will learn:

How to apply length-constraint method

How to differentiate the length equation to get velocity relations

How to find the upward speed of mass M

Why the motion of the ends forces the block to move

How angles affect velocity relations in strings

This is a classic constraint motion problem, often seen in JEE Advanced.

This video is perfect for:
✔ Class 11 Physics students
✔ JEE Main + Advanced aspirants
✔ NEET Physics aspirants wanting strong mechanics fundamentals
✔ Anyone who wants deep conceptual clarity in Newton’s Laws + Constraints

By the end of this video, you will confidently solve multi-string, multi-pulley, constraint-based problems using logic—not memorization.
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Topics covered: constraint motion, pulley and string problems, tension and acceleration, unstretchable string, velocity relations in pulleys, JEE Advanced mechanics, class 11 physics, Newton’s laws of motion, constraint equations, FBD with constraints, multi-block systems, advanced problem solving physics.