Kinematics lessons for Cambridge IGCSE Physics

In the IGCSE syllabus

1. Lesson 4 · Extended papers onlyScalars vs Vectors

   Current has a direction, so why is it a scalar?

   Syllabus details

   Syllabus: 1.1 Physical quantities and measurement techniques, Supplement 4 (scalar and vector); 1.1 Supplement 5 (scalars: distance, speed, time...); 1.1 Supplement 6 (vectors: velocity, acceleration, force...)

2. Lesson 9 · Extended papers onlyWhat Is Acceleration? Why It's 180, Not 20

   You gain 30 points in 120 days, your friend gains 10 points in 10 days. Who improved faster?

   Syllabus details

   Syllabus: 1.2 Motion, Supplement 9 (define acceleration, a = Δv/Δt); 1.2 Supplement 11 (acceleration from the gradient of a speed-time graph)

Partly in the syllabus

Only part of the lesson is in the syllabus. Each lesson says which part.

1. Lesson 3Instant vs Time Interval

   Is "the 3rd second" a moment or a stretch of time?

   Syllabus details

   Syllabus: 1.1 Physical quantities and measurement techniques, Core 2 and Core 3

   In it: Measuring time intervals with clocks and timers, and averaging a short interval over many repeats, are listed. Not in it: Nothing separates an instant from a time interval, or explains why 'the 3rd second' is a stretch.

2. Lesson 5Distance vs Displacement

   Run a full lap on a 400 m track: is your displacement 400 m or 0?

   Syllabus details

   Syllabus: 1.2 Motion, Core 1 (speed = distance travelled / time); 1.1 Supplement 5 (distance is a scalar)

   In it: Distance (path length) is listed, as the quantity inside speed. Not in it: Displacement as a change in position is not listed. The word 'displacement' only appears for measuring volume.

3. Lesson 6Average Speed vs Average Velocity vs Instantaneous Velocity

   Two taxi rides to the same place: 7.5 km in 14 min, or 10 km in 15 min. Which one is faster?

   Syllabus details

   Syllabus: 1.2 Motion, Core 2 (velocity = speed in a given direction); 1.2 Core 3 (average speed = total distance / total time)

   In it: Speed, velocity and average speed are listed. Not in it: 'Average velocity' and 'instantaneous velocity' are not named, so the difference between them is not tested directly.

4. Lesson 7How to Find Average Velocity of a Multi-Part Trip

   A car covers 1/4 of the trip at 20 m/s and the rest at speed v. The whole-trip average velocity is 16 m/s. What is v?

   Syllabus details

   Syllabus: 1.2 Motion, Core 3 (average speed = total distance / total time)

   In it: Total distance divided by total time is listed, which is the method for a trip in several parts. Not in it: Average velocity (total displacement / total time) is not listed, only average speed.

5. Lesson 8How to Find Change in Velocity: Why It's 7, Not 3

   A ball hits the ground at 5 m/s and bounces up at 2 m/s. Is its change in velocity 3 m/s or 7 m/s?

   Syllabus details

   Syllabus: 1.2 Motion, Supplement 9 (acceleration = change in velocity per unit time, a = Δv/Δt)

   In it: Change in velocity appears only inside the Extended definition of acceleration. Not in it: Finding Δv with signs and direction, such as a ball bouncing back, has no entry of its own.

6. Lesson 10Speeding Up or Slowing Down? Check a and v

   A car's acceleration keeps getting smaller. Is it speeding up or slowing down?

   Syllabus details

   Syllabus: 1.2 Motion, Core 5(c)(d) (decide from a graph if accelerating or decelerating); 1.2 Supplement 12 (deceleration is a negative acceleration)

   In it: Telling speeding up from slowing down on a graph, and that deceleration is a negative acceleration, are listed. Not in it: The rule 'a and v in the same direction means speeding up, opposite means slowing down' is not stated.

Not listed as a separate topic

These are basic ideas that the later lessons build on, so they are still worth watching first.

1. Lesson 1Point Mass (Particle) Explained

   Can a walking cat be treated as a particle?

2. Lesson 2Frame of Reference & Coordinate System

   Sitting still on a speeding subway: are you moving or not?