Beam bridges are the cheapest type of bridge to make. They are the most simplest to construct compared to the others. The simplest form of a beam bridge would if you took a board of any size and placed it over two desk that are closer than the boards length. If the gap is to great or too much of a load is added then the board will sag greatly. This may be solved if, the thickness of the board is increased or there are supports that are put in.

The arch bridge is one of the oldest forms of a bridge. It is like a inverted suspension bridge, with all the tension replaced by compression, and vice versa. There are differences in the stability of the system. An example would be if you, hung a rope across a gap, and it will return to its original position, after some oscillation

Forces also produce acceleration. This is extremely important in structures because there are live loads - people walk across upper floors, trains and vehicles go across bridges, and the wind can blow from any direction. These forces can set the structure vibrating at its resonant frequencies - the ones at which it naturally oscillates. If the forces vary at one of the resonant frequencies, things can go wrong. Breaking step on a small, flimsy bridge is good idea. Even worse, more than one resonant frequency could coincide. Worse, still, a small but fairly steady force can produce oscillations because of the interaction of the structure with the air. Tacoma Narrows bridge is only the most famous example of several collapses. This is an extreme example - in fact the effects of forces are never instantaneous - they always take time to propagate through the medium. As the speed of waves in structural materials is so high, we are normally not aware.

Suspension bridges are the light and strong and can span distances of 2,000 to 7,000 feet, which is far longer than any other type. Though they are very good they are the most expensive. What a suspension bridge does it suspends the roadway from huge main cables, which extend from one end of the bridge to the other. The towers enable the main cables to be draped over long distances. Most of the weight of the bridge is carried by the cables to the anchorages, which are imb

Some common words found in the essay are:
Bridges Bridges, Compression Tension, Tacoma Narrows, physics bridges, compression tension, resonant frequencies, main cables, structural materials, suspension bridge, arch bridge, suspension bridges,
Approximate Word count = 971
Approximate Pages = 4 (250 words per page double spaced)