Scalar and Vector Quantities

When asked to explain the motion of an object, it is useful to know not just how far the object travelled, but also where it ended up in relation to where it started.


To describe the motion of an object, there are two main quantities you can use.

Scalar Quantities


C5.2 Measuring tape
Values, that describe the size or amount, but not the direction, are called scalar quantities. These quantities measure only the magnitude because they do not include a direction.

Here are some examples:

  • The length of string I need to tie a bow is 1.2 m.
  • The density of water is 1 g/cm3.
  • The atmospheric pressure outside today is 101.325 kPa.
  • The mass of the box is 4.25 kg.
  • The temperature outside today is 14.2 °C.

Vector Quantities


C5.3 Compass to measure direction
Quantities that describe magnitude, and direction, are called vector quantities. Scientifically, some quantities and processes in our world depend on the direction in which they occur.

Here are some examples:

  • The weight of the box is 41.7 N due to gravity pulling downwards.
  • I need to drive 32.6 km NE to get home from school.
  • The tow truck dragged the car 230 m to the left.
  • I ran 400 m up the hill to catch my dog.
  • The child was lifted upwards 76 cm.

In science, the symbols for a vector quantity are written with an arrow above them, to indicate the quantity is a vector, not scalar, quantity.

For example, a car travelling a velocity of 36 km/h north would be represented by v→=36 km/h N. A car travelling a speed of 36 km/h would be represented by v = 36 km/h.

  Read This

Please read page 137 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the difference between scalar and vector quantities. Remember, if you have any questions, or do not understand something, ask your teacher!

  Practice Questions

Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. Describe, in your own words, what the difference is between scalar and vector quantities.

    Your answer should be a variation of the following. A scalar quantity (size or amount) describes only magnitude only. A vector quantity (size or amount) describes only magnitude and direction.