physics-tutor（物理导师）

Physics Subject Expert

Specialized knowledge for physics studying, problem-solving, and note creation.

Topic Coverage

mindmap
  root((Physics))
    Mechanics
      Kinematics
      Forces & Newton's Laws
      Energy & Work
      Momentum
      Rotational Motion
    Electromagnetism
      Electric Fields
      Circuits
      Magnetism
      EM Waves
    Thermodynamics
      Heat & Temperature
      Laws of Thermo
      Entropy
    Waves & Optics
      Wave Properties
      Sound
      Light & Optics
    Modern Physics
      Relativity
      Quantum Mechanics
      Nuclear Physics

Quick Reference Links

• Formulas and Constants: See formulas.md
• Mechanics Problems: See mechanics.md
• Electromagnetism: See electromagnetism.md

Diagram Patterns

Free Body Diagram (ASCII)

                 N (Normal)
                 ↑
                 │
    f ←─────────┼─────────→ F (Applied)
    (friction)  │
                │
                ↓
                W (Weight = mg)

Vector Addition

flowchart LR
    A[Vector A] --> C[Resultant R]
    B[Vector B] --> C

Circuit Diagram (ASCII)

    ┌────/\/\/\/────┐
    │      R        │
  ──┴──           ──┴──
  + │ -  Battery   │
  ──┬──           ──┬──
    │               │
    └───────────────┘

Problem-Solving Framework

General Steps

1. Draw a diagram - Visualize the situation
2. List knowns and unknowns - Organize given data
3. Choose equations - Match variables to formulas
4. Solve algebraically first - Keep symbols until the end
5. Substitute values - Include units
6. Check answer - Units, magnitude, direction

Kinematics Problem Pattern

Given: v₀, a, t (or any 3 of 5 variables)
Find: x, v (or remaining variables)

Equations to choose from:
1. v = v₀ + at
2. x = v₀t + ½at²
3. v² = v₀² + 2ax
4. x = ½(v₀ + v)t

Force Problem Pattern

1. Draw free body diagram
2. Choose coordinate system
3. Apply ΣF = ma in each direction
4. Solve system of equations

Key Concepts Summary

Newton's Laws

Energy Conservation

$$E_{total} = KE + PE = \text{constant (in isolated system)}$$

$$KE = \frac{1}{2}mv^2 \quad PE_{gravity} = mgh \quad PE_{spring} = \frac{1}{2}kx^2$$

Momentum Conservation

$$p = mv \quad \Sigma p_{before} = \Sigma p_{after}$$

Common Mistakes to Avoid

1. Forgetting to convert units (km to m, hours to seconds)
2. Wrong sign convention (acceleration vs. deceleration)
3. Using wrong kinematic equation (check which variable is missing)
4. Ignoring friction when it's present
5. Confusing instantaneous vs. average values