in this video we're going to explore two different types of force contact forces and non-contact forces and we'll look at some examples of each first though we need to be comfortable with the term force itself we can describe a force as a personal pull that acts on an object due to its interaction with another object and we measure force in newtons for example when a hand which is one object pushes a box which is another object it exerts a force like five newtons as well as this magnitude though which we're measuring in newtons forces also have direction so we could say that this force is acting to the right this means that forces are classed as vector quantities because they have both magnitude and direction now all forces can be divided into two different groups contact and non-contact forces and the key difference between the two is that contact forces are those where the two objects are physically touching whereas non-contact forces are those that don't require the two objects to be touching for example the friction between this board and the sand is a contact force because the board and the sand have to be touching for the friction to act similarly air resistance is a contact force because the object in this case the dog's face has to come into contact with the air particles in order to feel the resistance tension is a bit more difficult to explain but it's basically the pulling force that's being exerted through the rope the last contact force to know is the normal contact force which is also sometimes known as the reaction force in this picture we can see a rock on a table and because the rock has mass will be exerting a force downwards which is weight to keep it in position though and stop it from falling the table must be exerting an equal and opposite force upwards and it's this force that we call the normal contact force now non-contact forces don't have to be touching and so they can act through empty space the three types you need to know are gravitational force magnetic force and electrostatic force when we talk about these non-contact forces we often talk about them as fields of influence around an object because the forces can act on anything in that surrounding area for example gravity is a force of attraction between any two objects that have mass like the earth and you or me but importantly we'd still feel this force of attraction even if we weren't touching the earth magnetic forces can be attractive or repulsive depending on the poles of the magnets and we'll cover this in another video finally electrostatic forces which are between charged objects can also be attractive or repulsive and again i covered in another video for all of these non-contact forces though the strength of the force will decrease as the objects get further apart that's everything for this video though so i hope you found it useful and we'll see you next time