Physical Quantities and Measurement Techniques Lesson PlanIGCSE Physics 0625 · for teachers, tutors and self-study

Write the four questions on the board. Give students a minute per question to write an answer in their exercise books, then take two or three answers aloud with reasons. Do not correct question 3 yet — take a show of hands for "time one swing" against "time many swings" and come back to it in the next stage. For question 4, ask for a hand signal: one finger for speed, two for velocity.

Write a short answer to each question in your exercise book, then hold it up or tell a partner when asked (mini whiteboards work too, if your class has them).

Rulers and cylinders (4 min). Draw a measuring cylinder on the board with the water at $34\,\text{cm}^3$ and again at $51\,\text{cm}^3$ after a stone is added. Model the routine: work out what one small division is worth, read at the bottom of the meniscus with the eye level with it (no parallax), record to the resolution of the scale, then subtract: $51 - 34 = 17\,\text{cm}^3$. (Optional: do it for real with a measuring cylinder and a stone.) Then walk through Worked example 1: Reading a measuring cylinder and finding a volume by displacement.

Measuring multiples (4 min). A ruler can only read to $1\,\text{mm}$, so one coin's thickness cannot be measured well. Stack $25$ coins: the stack is $4.6\,\text{cm}$, so one coin is $4.6 \div 25 = 0.18\,\text{cm}$. Point to Worked example 2: Measuring multiples: the diameter of one bead for the same idea.

Pendulum period (4 min). Swing a string-and-weight pendulum (optional; otherwise sketch it and describe it). Show one complete oscillation: from one side to the other and back. Explain the method: let it swing with a small amplitude, start timing as it passes a fixed mark, count $20$ complete oscillations, repeat and average, then divide by $20$. Write a result on the board: $20$ oscillations take $31.4\,\text{s}$, so $T = 31.4 \div 20 = 1.57\,\text{s}$. Use Worked example 6: Period of a pendulum from repeated timings and Worked example 7: Measuring the length of a pendulum accurately. Return to starter question 3 and settle the vote.

Copy the measuring-cylinder sketch and the three rules (read the bottom of the meniscus, eye level, record to the scale's resolution). Write the multiples method and the pendulum method as numbered steps. If a pendulum is used, two students time $20$ oscillations each on a phone (optional) and the class compares the results.

Scalars and vectors (4 min). Draw two columns on the board, Scalar and Vector. Read the syllabus list aloud one quantity at a time (distance, force, speed, velocity, time, weight, mass, acceleration, energy, momentum, temperature, electric field strength, gravitational field strength) and ask students to point left or right before you write it in. Stress the pairs that catch students out: speed is a scalar, velocity is a vector; mass is a scalar, weight is a vector. Refer to Worked example 4: Scalars and vectors: definitions and classification.

Resultant by calculation (4 min). Forces of $6.0\,\text{N}$ east and $8.0\,\text{N}$ north act on a point. Sketch the two arrows tip-to-tail to make a right-angled triangle.

• Size: $F = \sqrt{6.0^2 + 8.0^2} = \sqrt{100} = 10\,\text{N}$.
• Direction: $\tan\theta = \dfrac{8.0}{6.0}$, so $\theta = 53^{\circ}$ north of east.

Stress that a vector answer needs a direction, and that $6.0 + 8.0 = 14\,\text{N}$ is wrong because the forces are not in a line. See Worked example 8: Resultant of two forces at right angles by calculation.

Resultant by scale drawing (4 min). A plane flies north at $120\,\text{m/s}$ in a wind blowing east at $35\,\text{m/s}$. Choose a scale ($1\,\text{cm} = 10\,\text{m/s}$), draw $12\,\text{cm}$ north then $3.5\,\text{cm}$ east from its tip, join start to finish and measure: about $12.5\,\text{cm}$, so $125\,\text{m/s}$, at about $16^{\circ}$ east of north. Draw it on the board with a board ruler, or a long straight edge. See Worked example 9: Resultant velocity by scale drawing.

Point left (scalar) or right (vector) for each quantity, then copy the completed table. Copy the calculation, then draw the plane's scale diagram in your exercise book with your own ruler (optional: a protractor for the angle; without one, find the angle from your two measured sides with the tangent ratio) and compare your answer with a partner.

Read each question aloud and write the numbers on the board. For question 1 (multiple choice), students show fingers $1$ to $4$ for A to D; for question 2 (true or false), thumbs up or thumbs down. For the rest, students write the answer in their exercise books and hold them up on your signal (mini whiteboards, if available). Use the responses to decide who starts on the support tasks in the next stage. For question 5, ask for a sense check: more oscillations than seconds means each one takes less than $1\,\text{s}$.

Answer with a hand signal or in your exercise book and hold it up when asked.

Write the three questions on the board. Students work through them in order and move on when they are confident; students who struggled in the guided practice start on the support tasks (see Support and stretch). For the Core question, if you have a pendulum and phones (optional), groups can collect their own three timings instead of using the data given. Circulate and check that Extended answers include a direction and that the river crossing uses the across-river speed for the time. Early finishers move to the Practice Exam Questions for this subtopic.

Work through the Core, Extended and Challenge questions in your exercise book, showing full working and units. Then continue with the Practice Exam Questions.

Write the three exit-ticket questions on the board. Students answer on a page torn from their exercise books (or a slip of scrap paper) and hand it in. Sort the answers into three piles (all correct / one wrong / two or more wrong) to plan the start of the next lesson. Finish by asking the class to describe one complete oscillation aloud — from one side, to the other and back.

Answer the three questions on your own, then check them against the success criteria at the top of the lesson.