Physics: how to show steps for derivations and numericals?

How to Show Steps for Derivations 

A derivation is like telling a story that starts with a fundamental principle and ends with a final formula.

1. State the Aim: Begin by writing what you intend to derive.
   • Example: "To derive the expression for the equivalent resistance of three resistors connected in parallel."
2. Draw a Neat, Labelled Diagram: This is crucial and often carries marks. A large, clear diagram helps the examiner understand your approach instantly. Label all components, variables, and directions (like current or forces).
3. State Principles and Assumptions: Mention the fundamental law you are applying.
   • Example: "According to Ohm's Law..." or "Applying Kirchhoff's junction rule at node A..." Also, state any assumptions, like "For a thin lens..." or "Assuming the collision is perfectly elastic..."
4. Show Logical Mathematical Steps:
   • Write each step clearly. Don't skip important algebraic manipulations.
   • Number your main equations (1), (2), (3)... so you can refer back to them easily.
   • Briefly state the reasoning where needed, like "Substituting eq. (1) into eq. (2)..."
5. State the Final Result: Conclude with the final derived expression. Put a box around it to make it stand out and clearly define the variables used.

How to Show Steps for Numericals 

For numericals, the best practice is the G-F-F-S-A method. It's clean, organized, and ensures you don't miss any steps.

1. G - Given: List all the data provided in the question with their proper symbols and SI units.
   • Example:
     • Mass (m) = 2 kg
     • Initial velocity (u) = 10 m/s
     • Time (t) = 5 s
2. F - Find: Clearly state the quantity you need to calculate.
   • Example:
     • Find: Force (F) = ?
3. F - Formula: Write down the primary formula(s) you will use. This step alone can fetch you marks.
   • Example:
     • v = u + at

     • F = ma

       

4. S - Solution (Substitution & Calculation):
   • First, show the given values substituted into the formula. This is a critical step.
   • Then, show the step-by-step calculation.
   • Example:
     • a = (v - u) / t(Here we first find 'a')
     • a = (0 - 10) / 5 = -2 m/s²
     • F = 2 kg × (-2 m/s²)
5. A - Answer: State the final answer clearly with the correct SI unit. Put a box around your final answer.
   • Example:
     • F = -4 N