Teachers Notes

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The important thing to understand is a Scalar quantity has magnitude only, whereas a Vector quantity has both magnitude and direction. An example of where this can cause confusion is when considering speed and velocity; particularly when looking at circular motion where an object is moving with the same magnitude of speed but its velocity is constantly changing (because its direction is constantly changing).

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A key skill for students to learn is how to draw vectors both to scale and in the correct direction (this becomes very important for students to understand when you have multiple vectors i.e. when looking at resultant forces); we recommend you allow time for students to learn this skill.

 

An object with a changing velocity is, by definition, accelerating and, if accelerating, it must be experiencing some kind of force.

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In Physics it is quite normal to have formulae where you multiply a scalar by a vector; Force=mass x acceleration for example. In this example mass is a scalar (as there is no direction component to mass) and acceleration is a vector (because it has magnitude and direction). The important thing to realise, here, is that Force is a vector quantity because whenever you multiply a scalar by a vector, the result is always a vector quantity.

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For the majority of subjects (and in text books) at KS4/GCSE, speed and velocity are readily interchanged. However, if you have students who plan to study A Level Physics and beyond, we would advise to be disciplined about how speed and velocity are used (and other Vectors such as Acceleration, Displacement, Force, Momentum)

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If you have any queries then please email us.

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