Lesson Plan

• Describe the concept of a physical quantity as a product of a numerical magnitude and a unit.
• Identify base SI units for common quantities and explain their symbols.
• Distinguish between base and derived quantities and correctly write them with appropriate units.
• Apply correct unit usage to solve simple physics problems and avoid common mistakes.

• Projector and screen
• Whiteboard and markers
• Printed worksheet with practice questions
• SI units reference chart (poster or handout)
• Ruler, balance, and stopwatch for demonstration
• Laptop with presentation slides

Begin with a quick demonstration: show a ruler, a balance, and a stopwatch, asking students what each measures. Recall that previous lessons covered measurement and the importance of accuracy. Explain that today they will see why pairing the measured number with the correct unit is essential for meaningful physics. Success will be measured by correctly expressing quantities in SI units during practice.

1. Do‑Now (5’) – Students write the unit for a list of quantities on a sticky note; teacher checks for completeness.
2. Mini‑lecture (10’) – Introduce Q = N × U, explain numerical magnitude vs. unit, and review SI base units using slides.
3. Guided practice (12’) – Work through examples of expressing length, mass, time, and force on the board, highlighting common mistakes.
4. Collaborative activity (15’) – In pairs, students use rulers, balances, and stopwatches to measure objects, then record each measurement with correct units on a worksheet.
5. Derived quantities demo (8’) – Show how velocity, acceleration, and force are derived, converting formulas into unit expressions.
6. Formative check (5’) – Quick quiz (exit ticket) where students write the unit for a given derived quantity.

Summarise that every physical quantity must be written as a number together with its unit, and that using the SI system ensures consistency. Students submit their exit tickets, which will be reviewed for understanding. For homework, assign the three practice questions from the notes, asking them to show full unit work.