Scalars & Vectors

Scalars are quantities with a magnitude (size) only. Vectors have a magnitude (size) and a direction.

Speed vs Velocity

• Speed is a scalar.
  • Speed describes how fast something is travelling but says nothing about direction.
• Velocity is a vector.
  • Velocity describes how fast something is going and in what direction.

Distance vs Displacement

• Distance is a scalar.
  • Distance describes how far something has travelled.
• Displacement is a vector.
  • Displacement describes the distance from one place to another.
  • Displacement also describes the direction from the start to the end.
• E.g. If an ant travels 6 metres east then 2 metres west:
  • Distance = 8 metres.
  • Displacement = 4 metres east.

Mass

• Mass is a scalar.
  • Mass describes how much of something there is.
  • Mass has no direction.

Acceleration

• Acceleration is a vector
  • We must know the magnitude (how quickly something is speeding up) and the direction (in which direction it is speeding up).

Force

• Force is a vector.
  • We need to know the magnitude (size) of the force and also the direction it acts.
• Weight is an example of a force and so weight is a vector.