Takes Two to Topple - Page 8

BALANCE

Did you find a relationship between the center of gravity and whether a structure STANDS? Look carefully at the vertical (up-and-down) thin black line and the base of the structure. Here are a couple of examples for comparison:

Xsectsnap6 STANDS Xsectsnap10 TOPPLES

For structures that STAND, the vertical line goes through the base!

For structures that TOPPLE, the vertical line does NOT go through the base!

Some structures have the vertical line very close to the edge of the base. If the line does go through the base, the structure should still STAND, although it may be difficult to get it to do so! For the examples below, the edge of the base is located at 9.5 (in the X direction, halfway between columns 9 and 10). In the first case, the center is at 9.44, which is less than 9.5 and above the base, so the structure will STAND. In the second case, the center is at 9.52, which is more than 9.5 and past the base, so the structure will TOPPLE.

Xsectsnap7 Center: 9.44, 9.56
STANDS
Xsectsnap8 Center: 9.52, 9.56
TOPPLES

We can now make our final hypothesis for the behavior of a structure is:


A structure will STAND when its center of gravity is located directly above its base, and TOPPLE when the center of gravity is not above the base.


Well done! With this insight and some practice, you should now be able to make a fairly good prediction about whether something will STAND or TOPPLE, before testing it to see! Your career as an engineer is underway!



Further Exploration Questions