PART–4 (viii) : IIT / JEE Previous Year Questions – Mixed Traps & Mastery Set
This set focuses on subtle traps, boundary cases, and method switching. These are the questions that usually differentiate top ranks from average scores.
PYQ–36 (IIT–JEE Advanced)
Question:
A block of mass m is kept on a rough horizontal surface. A horizontal force F is applied gradually from zero. Describe the nature of friction as F increases.
Method Selection:
Conceptual analysis of static and limiting friction.
Solution:
Initially, friction equals the applied force and increases with F.
When friction reaches its maximum value μsmg, the block is on the verge of motion.
After motion starts, friction becomes kinetic and remains nearly constant.
Examiner’s Intention:
To check understanding that friction is not always μmg.
PYQ–37 (IIT–JEE Advanced)
Question:
A body is thrown vertically upward. At what point is the net force on the body minimum?
Method Selection:
Analyze forces during upward motion ignoring air resistance.
Solution:
Throughout the motion, only gravitational force acts.
Net force = mg (constant).
Hence, net force is same at all points; no minimum or maximum.
Examiner’s Intention:
To trap students who think force changes with velocity.
PYQ–38 (IIT–JEE Advanced)
Question:
Two blocks are connected by a string over a smooth pulley. If the string suddenly breaks, describe the motion of both blocks immediately after.
Method Selection:
Apply Newton’s First Law (instantaneous response).
Solution:
Immediately after the string breaks, blocks continue with their instantaneous velocities.
Subsequently, only gravity acts and they follow independent motion.
Examiner’s Intention:
To test understanding of inertia and instantaneous effects.
PYQ–39 (IIT–JEE Advanced)
Question:
A body is moving with constant speed but changing direction. What can be said about work done by the net force?
Method Selection:
Use work–energy theorem.
Solution:
Kinetic energy remains constant.
Hence, net work done by force is zero.
Examiner’s Intention:
To connect Laws of Motion with energy concepts.
PYQ–40 (IIT–JEE Advanced)
Question:
A block is placed on a weighing machine inside a lift. Suddenly the cable snaps. What reading does the machine show?
Method Selection:
Analyze free-fall condition.
Solution:
During free fall, acceleration = g downward.
Normal reaction = 0.
Hence, the weighing machine reads zero.
Examiner’s Intention:
To test extreme case of apparent weight.
Master Traps & Final Guidance
- Force depends on acceleration, not velocity.
- Static friction adjusts itself up to a maximum value.
- Instantaneous motion follows inertia.
- Constant speed does not mean zero force.
- IIT loves boundary and extreme cases.
PART–4 (viii) Completed.
Total PYQs covered: 40+
Laws of Motion is now fully competitive-ready for IIT–JEE Advanced.
📚 Physics Thinking Library – How IIT Toppers Think
Welcome to the Physics Thinking Library by Mind Grow Magazine. This library is specially designed for IIT–JEE & Intermediate students to understand how toppers think, decide, and solve Physics problems.
🎯 What You Will Learn From This Library
- How IIT toppers approach Physics questions
- Decision-making during problem solving
- Common traps & how to avoid them
- Exam-hall mindset and logic flow
- Step-by-step thinking framework
📘 Complete Series: How IIT Toppers Think (Part 1–25)
Click on any part below to start learning. It is recommended to read in order.
- Part 1 – Introduction to Topper Thinking
- Part 2 – Understanding the Problem Statement
- Part 3 – Visualization & Physical Sense
- Part 4 – Role of Acceleration & Forces
- Part 5 – Free Body Diagram Thinking
- Part 6 – Method Selection Strategy
- Part 7 – Avoiding Formula Traps
- Part 8 – System Approach Mindset
- Part 9 – Friction & Constraint Thinking
- Part 10 – Time vs Accuracy Balance
- Part 11 – Common Thinking Mistakes
- Part 12 – Decision Flow in Tough Problems
- Part 13 – Eliminating Wrong Options
- Part 14 – Handling Multi-Concept Questions
- Part 15 – Pressure Handling in Exam Hall
- Part 16 – Speed Building Without Guessing
- Part 17 – Extreme Case Thinking
- Part 18 – Logical Shortcuts vs Blind Tricks
- Part 19 – Advanced Reasoning Techniques
- Part 20 – Rank-Deciding Thought Patterns
- Part 21 – Physics Intuition Development
- Part 22 – Eliminating Panic in Tough Questions
- Part 23 – Last-Minute Thinking Strategy
- Part 24 – Mistake-Proof Problem Solving
- Part 25 – Final Topper Framework
🧠 How to Use This Library Effectively
- Read 1–2 parts daily
- Apply thinking to real Physics problems
- Revisit library before exams
- Use as a mindset guide, not memorization
This library is a long-term asset for serious Physics learners.
© Mind Grow Magazine
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