Bridge Pix-2000 
          Mark Fischer
     Assistant Professor of Physics
Department of Chemistry and Physical Sciences


Design and build a bridge to the following specifications:
  • Bridge must span a 25 cm chasm. (This means your bridge must be LONGER than 25 cm). See Fig. 1.
  • Bridge may be UP TO 7 cm wide. See Fig. 2.
  • Bridge MUST have a space, at the center of the span, to allow the placement of the Mass Hanging Bracket, see Figs. 1 and 2. The bracket, shown in Fig. 3, may be placed parallel or perpendicular to the bridge. Either way, there must be a gap of at least 3 cm x 3 cm for the loop of the Mass Hanging Bracket.
  • Bridge must be LESS THAN 18 g. This largely limits the construction materials to balsa wood. It would be wise to weigh your materials before you start building, and remember that glue adds mass!
Figure 1: The Span

 
 

 Figure 2: Max Width

Figure 3: Mass Hanging Bracket

 

Schedule:

Week of 6 November:
Consult the library and/or the Web for materials on bridges.
Make a ROUGH SKETCH of one or more designs you are considering.
Have your instructor sign your drawing.

Week of 13 November:
Make a SCALE DRAWING of your final design.  The drawing should include a SIDE VIEW and a TOP VIEW.  It is perhaps easiest to make the drawing full-sized on graph paper. You can then use the drawing as a template for constructing the bridge.  Again, have your instructor sign your drawing.
By this time, you should have also secured materials for your bridge.

Week of 20 November: 
Bring FINISHED bridge to lab to be tested.
Bridge MUST be complete at this time…THERE WILL BE NO LATE ENTRIES!
 
 
 

Scoring:

Your bridge’s performance will determine your score for this lab.

 Rough Drawing by week of 6 Nov1 point
 Scale Drawing by week of 13 Nov 2 points
 Completed Bridge by week of 20 Nov 3 points
 Bridge Meets All Specifications 1 point If the bridge meets all specs, then weights will be slowly added to the hanging bucket until the bridge fails. It will be scored by calculating the following ratio: Score = (Mass Supported) / (Mass of Bridge).  Bridge holds AT LEAST 1 kg 1 point
 Bridge holds from 2kg up to 1000 times its mass (Score < 1000) 1 point
 Bridge holds more than 1000 times its mass (Score > 1000) 1 point

Total: 10 points
The Rules
circa 2000
There are as many different sets of bridge specifications as there are bridge building competitions.

Here's what we used...
this time around.