Scalars and vectors
This lesson belongs to Cambridge International IGCSE Physics 0625. It is not part of the Egyptian Baccalaureate / Thanaweya Amma syllabus and is not a Year 3 course. The whole lesson is Supplement content for Extended candidates; Core candidates can skip it.
Start with the key question: does direction matter?
A magnitude is the size or amount of a quantity. A scalar needs magnitude only. If I say “the lesson lasts 40 minutes”, you know the time without needing a direction. Distance, speed, time, mass, energy and temperature are scalars.
Open the worked example
“The runner travels 200 m” gives a distance. It is complete as a scalar description. “The runner travels 200 m north” adds a direction, but distance itself remains scalar.
Quick check: Does a scalar need a direction to be fully described?
Think, then reveal: No. A scalar has magnitude only.
Build the resultant vector
Explore a right-angle resultant
Change the east and north components. The blue arrows show the two velocities; the red arrow is their resultant. The model measures angle east of north.
R = √(3² + 4²) = 5.00 m/s · angle = 36.9° east of north
For this right triangle, adding the component sizes directly would give the wrong diagonal length.
Practise, then read the explanation
Use the optional hint if you need a nudge. Submit an answer to see the reasoning, or switch to study mode to review.
Optional hint
Ask whether a direction is needed to describe the quantity completely.
This original lesson and practice set are aligned to Cambridge IGCSE Physics 0625 Supplement objectives 1.1.4–1.1.7. The source PDF provides the fuller reading; references above identify the matching pages. In this lesson, resultants are calculated for perpendicular vectors as shown in this syllabus section.