Let’s talk forces. The world around you is forever changing; it could be because of entropy or because the world around you is full of very busy things that need to get on with their day. Regardless, your body constantly experiences forces that, because you’ve been living here awhile, you’re accustom to. Before we get into the types of forces, let’s apply some force to a seat while you put your bum in it as we look at what a force actually is.
A force is an interaction between two objects that results in one pushing or pulling the other. When you walkk, the sensation of the ground under your feet is a force that is due to the interaction. The wind you feel on your hand as you hold it out of the car and pretend to fly, that’s a force. A force only occurs during an interaction and once that interaction no longer occurs, neither does the force. There are two types of forces that forces are broken up into; Contact and Non-Contact (action at a distance) Forces.
As the name suggests, a contact force (CF) is something that results from the physical interaction of matter whereas a non-contact force (NCF) is an interaction that occurs without physical contact; it usually interacts with a field which we’ll look at more detail later. The types of CFs include normal, applied, friction, tension, spring and air resistance.
This is a force that just existence, usually, because of something resting on top of another. Think of a text book on a table; the table is supplying a force up onto the textbook to keep in there instead of it falling through it. Just like how the Earth supports you under your feet.
As the name suggests, this is a force that is applied to something regardless if it is on purpose or not. If you want to move something, you apply a force to it that makes it move if you can overcome the objects want to not move (inertia).
This is the force that is the interaction between two objects sliding over one another or wanting to slide. This can then be broken down into sliding friction when the object is moving and static friction when the force of friction is high enough to stop the object from sliding when on a slope.
This is the force that is experienced when a pulling action is applied to a rope or cable when dragging something. The rope is the medium for the applied force and therefore experiences tension force.
There is a big difference between tension force and spring force. Spring force is the force experienced between objects when a spring is either stretched or compressed. A spring wants to stay at its resting state so when it is stretched it pulls, and when it is compressed it pushes at both ends.
Air Resistance Force
This is the final CF that is to be discussed. This is the force that is experienced by all objects when they travel through the air. As something moves through the air (like your hand out the car window) the air particles collide with the object and move out of the way. If you’ve ever seen someone skydive with their mouth open, this is the work of air resistance.
These are interactions without physical contact and involves a phenomena known as fields. The types of NCFs include gravitational , electrical and magnetic forces.
Everything that has mass can experience a gravitational force. For us, this isn’t something that is felt or experienced on Earth because of Earth itself. It is the attraction that occurs between incredibly large objects on others; think about the effect the Earth has on you or on the moon. This is why we stay stuck to the planet instead of drifting into space, and why when something is thrown up, it must then fall down.
This is the force that is experienced between two objects that have a charged; whether it be positively or negatively charged. Opposites attract one another whereas objects of similar charge push one another away. Experiment! It is this force that, when you rub a balloon on your head, makes your hair stand on end or make little bits of paper dance when the balloon is held near.
This force is kind of similar to electrical force but magnetic force needs to have charged particles as well as a flow or movement and usually only occurs with metals. It has to do with the moving of charged particles that creates a magnetic force or field. Experiment! This can be seen by getting some cereal and holding a magnet to it. The metal components in the cereal will be attracted to the magnet and will move towards it over the milk.
Everyday you experience an array of stimuli that is considered normal; and it is. There are forces around you all of the time that allows for you to play basketball, move house as well as keep your feet flat on the floor…most of the time.