When we construct buildings (this applies for anything) we have to take into account that there is a driving force working against us, this force is known as gravity, this driving force pulls everything down ( or to the center of the planet) we also have to take into account Newtons Third law of motion which states that “ For every force acting on a body, The body exerts a force having equal magnitude in the opposite direction along the same line of action as the original force” This basically tells us that there has to be a balance between forces when we are constructing let’s say buildings. Structural elements all have to follow these base lies of rules. Structures like Coulms which help support the weight of an object above it. We must take into consideration that these objects are sturdy, so they don’t get crushed or buckle under their own weight. Beams must be sturdy enough, so they don’t cave in on loads bearing above them (bending stress), Arches have to be able to support a mass above them as well and be able to disperse the load, so they don’t slide apart.