S4.8.1 For the adult
Scalars and vectors
Mei walked 3 km east and then 3 km west. Did she go 6 km, or did she go nowhere?
What this chapter teaches
A scalar has a size. A vector has a size and a direction. Forces on one line add or take away. Forces at right angles make a triangle, and the resultant is its third side.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why is Mei back at her door after walking 3 km east and 3 km west, yet she walked 6 km?
- Two people pull a box in opposite directions, with 70 N and 45 N. What is the resultant, and which way does it point?
- Two forces of 30 N and 40 N act at right angles. Why is the resultant not 70 N?
After the chapter, the learner can
- Sort quantities into scalars and vectors
- Find the resultant of two forces along a line
- Add two forces at right angles with a scale drawing
What they copy into their notebook
A scalar has a size only. A vector has a size and a direction. On one line, forces add or take away. At right angles they make a triangle: 30 N and 40 N give 50 N.