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GCSE Physics Booster Tutor: Intro to forces & motion

Contact and non-contact. Scaler and vector

· GCSE Science Notes

The interaction between objects leads to actions which can be seen by the observer, these actions are caused by forces between the objects in question. A force is a push or pull.

Some of the interactions involve contact between the objects, where the objects are physically touching. These are called contact forces. An example of a contact force is friction. In the gif below the stickman is able to walk on the surface due to the friction (contact) between his feet and the surface. Put a layer of grease on the surface and friction is reduced and the stickman slips over.

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 Other examples of contact forces include air resistance, tension, and normal contact force. 


Other interactions involve no contact – the objects are physically separated. These are called non-contact forces. An example of a non-contact force is magnetic force. Below you can see the effect of the magnetic force bewteen the magnets but there is no contact between the objects.


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Other examples of non-contact forces are gravitational force and electrostatic force. 


When measuring forces, the physical quantities measured fall into two categories: scalars and vectors. Scalar and vector quantities are treated differently in calculations. 

Scalar quantities only have a magnitude or size. For example, energy (e.g. 100 J), mass (e.g. 15 kg), temperature (e.g. 10oC) or distance (e.g. 1m). 

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Vector quantities have both magnitude and an associated direction. For example, displacement (e.g. 2 m west), velocity (e.g. 23m/s upwards), acceleration (e.g. 9.8 metres m/s²downwards).


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Speed can be thought of as the rate at which an object covers distance. A fast-moving object has a high speed and covers a relatively large distance in a given amount of time, while a slow-moving object covers a relatively small amount of distance in the same amount of time. 

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Speed is also a scalar quantity, as it does not refer to direction. 

Speed can be calculated by knowing the values for distance and time. 

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