Measuring Quantities
In science we use lots of different measurements, we measure time, distance, volume, sound level, heart rate etc. These measurements all have different units,
Seconds are the standard unit for time, but sometimes we use minutes, hours, or even days, depending on what we are measuring.
Scalar Quantities
Simple measurements or measurements that do not have a direction are called scalar quantities. Things like time, mass, distance and speed do not have a direction.
If something in science has a quantity/size/magnitude but no direction we say it is scalar.
Vector Quantities
There are special quantities in science that have both a size and a direction.
We call these VECTORS.
With forces, direction is important, we always use arrows to show them, so force is a vector quantity.
Weight is related to gravity so it is a vector quantity.
Distance Vs Displacement
Distance is measured according to the amount of distance involved i.e. following a path:
Marble rolls= mm or cm (millimeters or centimeters)
Car travels= m or Km (meters or kilometers)
The first picture above shows the distance between point A and point B that the car travelled. The car has to stick to the roads- it can’t travel through buildings or peoples gardens.
The second picture shows the displacement between point A and point B, you can use a map to find this out. It is calculated in a straight line or ‘as the crow flies’ and needs a direction so a compass is used. In this example you would say that point B is 1.7 km south east of point A.
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