HOME : About DITC : Movie List : Links : Bibliography : Movie Comparison : Site Map : Search
Getting Started Select Design Task Learn About Design

Three Bridge Designs: V, Y and T

The bridge designs that most students create can be described by 3 letters of the alphabet: V, Y and T. The issue to keep in mind with each bridge type is that the vertical component of each bridge arm vector must total half of the load. If not, the bridge will fall. When you change the angle of the bridge's arms, the vertical and horizontal forces will also change. For the bridge to pass its test, the vertical force must counter the weight of the water bottle and results in a zero net force on the system.

Depending on its angle, the paper undergoes more or less stress. The deeper the angle (V), the more vertical force the diagonal arms supply. Designing a bridge with less steep arms (e.g., the Y design and even more for the T design), the paper pulls more horizontally (against itself). To produce the vertical force needed to support the bottle, the paper strip must pull harder.

It can do this up to a point -- its limit is the tensile strength of the paper. Once a critical angle is passed, the paper will give way before it can supply the force needed to hold up the water bottle.

Return To Top