Idea 5of 12Builds onStart to finish
Which way
Six metres, but six metres where?
Today you'll discover
- why a length alone cannot say where you end
- how arrows add when they point opposite ways
- the brackets physics writes after a unit
Think firstOne arrow, eight metres long
Is 'eight metres' enough to say where the arrow ends?
Answer first, then press Next. Read the bracket after each number: it says which way.
Arrows stacked over a metre scale, drawn one at a time. First a single warm arrow from a ring, eight metres long and unlabelled. Then its label, eight metres east, with the corner note that east is positive. Then a cool arrow begins under its head and runs two metres back to the left, labelled two metres west. Then a heavy lower arrow runs from the first ring to where the second arrow ends: six metres east. The last step shows two arrows pointing the same way and asks for start to finish.
See the whole ideathe big idea and the key word, in one place
The big idea
Six metres east. The direction is part of the answer.
Why it happensTwo metres west partly undoes eight metres east. Without the direction, eight and two could only ever add to ten.
Key word
- direction
- which way an arrow points, written in square brackets after the unit: [E], [W], [N], [S], [up], [down]
Ready to use it?
- Add two legs that point opposite ways, and keep the direction.