Static Equilibrium

Static Equilibrium is the physical state in which all components of a system are at rest and the net force is equal to zero throughout the system. When a system is in static equilibrium, it means that all the components of the system are not accelerating as a result of the net force equaling zero. An example of a system in static equilibrium is a game of tug of war.

This system of forces is considered to be in static equilibrium because the force that is being applied by the first man is equal to the opposite force being applied by the second man. Therefore, the sum of the forces, or the net force of the system, equals zero. Since the forces are balanced, it also means that there will not be any acceleration of the rope in either direction.

In addition, another characteristic of a system of forces that is in static equilibrium is that the system also has zero torque. Torque is a measure of the turning force on an object. Torque can be thought of as a twist to an object. An example of a system of forces that seems like it should be in static equilibrium is this diagram because te forces are balanced. However, there is torque in the system, which will cause the system to rotate.

My Bridge

When constructing my bridge I plan to produce a relatively basic truss bridge. By studying other successful balsa wood bridges on balsabridge.com I have found that the best bridges utilize either a truss or a piece of circular bent wood acting as a different type of truss. I decided to go with a truss because I believe that it is a slightly more basic structure type to understand and that it will be easier to construct. I took how easy the bridge was to construct into consideration because I wanted to try to decrease the percentage of error of my bridge failing as much as I possibly could. The design of my bridge looks much like this design:

I feel like this design was one of the best designs for constructing a balsa wood bridge because this is a strong truss design which will distribute the force that is applied by the weight nicely. In addition, this truss design is one that does not have an upright beam that is located at the midpoint of the bridge. This makes this design one that can be used for this particular project because if it were to have that upright beam at the midpoint then the metal rod that suspends the weight would not be able to be placed there.

Bridges

A bridge is a structure built to span physical obstacles for the purpose of providing passage over the obstacle. Bridges may be classified by how the forces of tension, compression, bending, torsion and shear are distributed through their structure. Here are a few of the many structure types.


Beam Bridge: Beam bridges are the most basic of bridge structures. They are made up of horizontal beams that are supported at each end. The earliest of beam bridges were most likely logs laid out across rivers or other gaps.

Arch Bridge: An arch bridge is a bridge with abutments, or structures built to support lateral pressure on each end shaped as arches. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. The earliest known arch bridges were built by the Ancient Greeks.

Truss Bridge: A truss bridge is a bridge that utilizes a truss in its a structure. This truss is a structure of connected elements forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. The truss bridge is one of the oldest structure types that are still commonly used today.

Suspension Bridge: Suspension bridges are suspended from cables. These cables are hung from towers that go very deep down into the ground. The earliest suspension bridges were made of ropes or vines covered with pieces of bamboo.