 # Different types of force

Different types of force is a topic that every cenineering student need to deeply absorb it. However this simple question of “what is a force?” might seems trivial, but it lay the foundation of civil engineering. In simple words force is an interaction between 2 different objects. when you press something, your hands are applying a force that is usually called pressure.

Forces are everywhere. Either you pull a rope, or walk on the street, in both cases you are applying a force. Amazingly even if you do nothing you are under the gravity force applied by the planet. We know this gravity force weight.

### Different types of force

Generally, some forces need physical contact to be applied, these are contact forces. the obvious example of contact force is when the boxer hit the bag. As soon as his punch touch the bag, the contact force occurs.

Other forces such as electromagnetism, and nuclear power are non-contact forces, which means they do not need contact to occur. this magnet, for example can effect on the iron from a distance. So no contact is required.

### How to define and measure a force

The second important question is How to quantify a force? Its obvious we need to report their magnitude, direction and point of application. These three parameters help us to quantify a force and represent it by drawing a vector. For example we can show the weight by drawing a downward vector.

Please bear in mind the gravity is always toward the centers of earth, and the length of this vector shows the amount of weight. once the magnitude and the line of application is determined we must find out at which point the force is applied. we usually assume that gravity affects at the centre of gravity of the object.

However in reality gravity is a distributed force affecting on every tiny particle of the object , but this simplification assumption makes the problem easier to solve. 