Scalars, vectors, adding and resolving
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 2 worked examples, 5 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- A force needs a direction
- Scalars and vectors
- Sort the quantities
Read the transcript of the teaching part
A force needs a direction
Push a door with ten newtons. Push it straight, and it swings open. Push along the hinge line, and nothing happens. The size is the same, so the direction must matter. Some quantities need both.
Scalars and vectors
A scalar quantity has magnitude only. Mass, energy, power, speed and distance are scalars. A vector quantity has both magnitude and direction. Force, weight, velocity, acceleration and momentum are vectors. Weight is a force, so it is a vector. Mass is a scalar. Power is never a vector. Two vectors cannot be added like ordinary numbers. We must account for their directions.
Sort the quantities
The pairs to learn. Scalars on the left: distance, speed, energy, power, pressure and density. Vectors on the right: displacement, velocity, force, momentum and acceleration. Pressure is a scalar even though it comes from a force.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Adding vectors · Resolving vectors · Scalars and vectors · Vector triangles.
The whole chapter: Forces, Density and Pressure, Physical Quantities and Units, Forces, Density and Pressure.
Chapter 1.1: Physical quantities
- Scalars, vectors, adding and resolving 5 min
- SI units, prefixes and homogeneity 5 min
Also for A Level Physics 9702
Which topics come up most in A Level Physics 9702 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.