(New tips are continually added to these pages. Check back in a few months' time for more)
TOPIC 1: Scalars and Vectors
For scalar quantities, eg. distance, speed, you only have to consider the magnitude but not the direction.
But for vector quantities, eg. displacement, velocity, you have to consider both the magnitude and the direction.
So if you walk 10 km to the North, and 8 km back South, the distance you have travelled is 18 km (just add 10 + 8). But your displacement is 2 km (10 km - 8 km), North (remember whenever you answer questions on vector quantities, you must include the direction otherwise marks may be deducted if your teacher is the very demanding sort).
Another example, if you walk 3 km North and then 4 km East, the distance you have travelled is 7 km (just add 3 + 4). But your displacement is 5 km (Pythagora's Theorem), 53.13º East of North (or bearing of 53.13º).
Another example, if you were cycling at 20 km/h towards the West, then turn around and cycle 30 km/h towards the East, your speed has changed by 10 km/h (just subtract 30 - 20). But your velocity has changed by 50 km/h, (30 -(-20)), Eastward.
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