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 Forces and motion

Physics is an interesting way of looking at things. Here we look at how physicists look at common concepts to do with distance and time.

Lets start with the units: in Physics, the standard (SI) units of:

  • Time are seconds (s), 60s in a min, 60 min in an hour(h)
  • Distance are metres (m), 100cm in a metre, 1000m in a kilometre (km)

Are you going anyhwhere? Distance and displacement

Distance is how far we have travelled. It doesn't matter where you end up but its the sum total of the metres (or other units) that you have covered.

Displacement: Displacement is distance travelled in a certain direction. With displacement, it matters where you end up. Displacement is simply summarised as the straight-line distance between the starting point and thefinishing point.

The diagram below illustrates the two.



Vector and scalar quantities

A vector quantity has both a magnitude (size) and a direction. Displacement is an example of a vector quantity. Other examples of vector quantities include:

  • Forces- a force has a size represented by the length of the arrow and a direction; where the arrow is pointing to.
  • Velocity- Velocity is Speed in a given direction e.g. Michael sets of in his car driving at 50km/h due north.

A scalar quantity only has a size. Examples include:

  • Speed
  • Mass