TOOTHPICK BRIDGES
OBJECTIVE
TO DESIGN AND BUILD A BRIDGE WHICH CAN BE TESTED FOR STRUCTURAL STRENGTH AND THEN ANALYZED FOR THE FORCES INVOLVED
MATERIALS
ROUND OR FLAT WOODEN TOOTHPICKS
ELMER'S WHITE GLUE
INSTRUCTIONS
EACH STUDENT WILL RESEARCH BRIDGE DESIGNS FROM LITERATURE OR ACTUAL STRUCTURES NOTING BRACING POINTS AND REINFORCEMENTS AND HOW EACH DESIGN TAKES INTO ACCOUNT GRAVITATIONAL AND LOAD FORCES AND THE MATERIALS USED.
EACH STUDENT WILL THEN DESIGN AND BUILD A BRIDGE USING WOODEN TOOTHPICKS AND ELMER'S WHITE GLUE
SPECIFICATIONS
THE TOTAL WEIGHT OF THE FINISHED BRIDGE CANNOT EXCEED
40 gmANY DESIGN CAN BE USED AS LONG AS THE ROADBED IS FLAT AND UNOBSTRUCTED TO ALLOW A MATCHBOX CAR TO TRAVEL ITS LENGTH.
THE BRIDGE MUST BE FREE STANDING AND ALLOW FOR A
2 cm X 30 cm BOARD TO PASS UNDER THE BRIDGE WHILE IT RESTS ON A FLAT SURFACE.ONLY THE MATERIALS LISTED MAY BE USED TO BUILD THE BRIDGE.
EXCESSIVE AMOUNTS OF GLUE MAY NOT BE USED AS PART OF THE STRUCTURE,
i.e. THE BRIDGE MAY NOT BE COMPLETELY COVERED WITH GLUE.
PROCEDURE
TO TEST EACH BRIDGE'S STRENGTH WE WILL PLACE THE BRIDGE ONTO AND BETWEEN TWO FLAT-TOPPED TABLES SPACED
25 cm APART.AN
8" WOODEN DOWEL WITH A 1/2" DIAMETER IS SET ACROSS THE MIDDLE OF THE ROADBED.TWO LOOPS OF STRONG CORD ARE ATTACHED TO THE HANDLE OF A
5 gal BUCKET.EACH LOOP OF CORD IS THEN LOOPED OVER EACH END OF THE DOWEL TO SUPPORT THE BUCKET BELOW THE BRIDGE.
SAND OR WATER IS ADDED TO THE BUCKET UNTIL THE BRIDGE BREAKS.
THE BUCKET AND ITS CONTENTS ARE THEN WEIGHED.
RANKING
EACH BRIDGE WILL BE RANKED USING A RATIO OF LOAD WEIGHT TO BRIDGE WEIGHT.
