The Physics of Bridges

There are many things to consider when building a bridge. A simple bridge that can be made is a beam bridge. One thing that should be taken into consideration when building a beam bridge are the beams on the bridge and the forces that act on them.

The forces on the beam bridge are the weight of the bridge and the reaction from the supports. As the weight pushes down on the supports we are going to assume that majority of the weight is in the center. With assuming this we know that the supports will have the same reaction.

Next we are going to try to add the forces. The vertical force (y-direction) is the force from the supports and the weight of the bridge while the horizontal force (x-direction) has none. Lets Assume the bridge has a weight of 500 Newtons. 

 F(y) is:  -500N + 4*F(support) = 0; solving for F(support) we will come out with 125N

F(x) is: There is none

F(x) + F(y) = 125N

So The supports each exert a force of 125 Newtons