Physics·General Physics · NSSCO 2.3.1
Position, distance & displacement
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Before we can talk about speed or velocity, we need three words kept carefully apart: position, distance and displacement. Position is where something is, measured from a reference point (and it can be positive or negative). Distance is the total path travelled — a scalar. Displacement is the straight line from start to finish, with a direction — a vector. We'll draw simple there-and-back journeys where distance and displacement come out completely different, and see why both are measured in metres.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 2.3.1):
- State that 'position' and 'reference point' are fundamental to studying speed, velocity and acceleration, and can be represented as x, y or z
- Recognise that a position, relative to a reference point, can be either positive or negative
- Define distance as a measure of how far an object travels along its path, without considering direction (a scalar, measured in metres)
- Define displacement as a vector: a magnitude equal to the shortest straight-line distance between the start and finish, with a direction from start to finish
- Work out and compare distance and displacement for simple there-and-back journeys, and give the units (m)
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Ms Elizabeth and Mike talk through the whole topic — with the figure and working drawn live.