Newton's Laws of Motion
Chapter: Mechanics | Difficulty: Medium–High | Avg JEE weightage: 2–3 questions/year
Subtopics
1. First Law — Concept of Inertia
Learned
2. Second Law — F = ma, Net Force
Learned
3. Third Law — Action-Reaction Pairs
Learned
4. Free Body Diagrams (FBD)
In Progress
5. Friction — Static & Kinetic
In Progress
6. Pulley Systems & Constraints
Not Started
7. Pseudo Force & Non-inertial Frames
Not Started
8. Connected Bodies on Incline
Not Started
Key Formulae
F_net = m × a
Net force = mass × acceleration. Vector equation. Apply along each axis separately.
f_s ≤ μ_s × N f_k = μ_k × N
Static friction can take any value up to μ_s·N. Kinetic friction is always μ_k·N once sliding.
For incline at angle θ: N = mg·cosθ, F_parallel = mg·sinθ
Resolve weight along and perpendicular to incline surface.
Atwood Machine: a = (m₁ - m₂)g / (m₁ + m₂)
Tension T = 2m₁m₂g / (m₁ + m₂). Assumes massless, frictionless pulley.
Problem Types in JEE
| Type | Description | Difficulty | Your Accuracy |
|---|---|---|---|
| FBD on horizontal surface | Find acceleration/tension with friction | Easy | 78% |
| Inclined plane with friction | Multiple blocks on incline, find motion | Medium | 52% |
| Pulley system (Atwood) | Connected masses, find accel & tension | Medium | 61% |
| Non-inertial frame (pseudo) | Apply pseudo force in accelerating frame | Hard | 33% |
| Multi-body constraint motion | Wedge + block, string constraints | Hard | 28% |
Common Mistakes (Your History)
| Mistake | Type | Count |
|---|---|---|
| Forgot to include friction when surface is rough | Concept error | 4 |
| Wrong direction of normal force on incline | Concept error | 3 |
| Arithmetic error in solving simultaneous equations | Calculation error | 2 |
| Missed tension component in FBD | Concept error | 2 |