SOLUTION: Can you explain why a three-legged stool is often more steady than a four-legged stool?

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Question 171836: Can you explain why a three-legged stool is often more steady than a four-legged stool?
Found 3 solutions by Alan3354, jim_thompson5910, Earlsdon:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Can you explain why a three-legged stool is often more steady than a four-legged stool?
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Yes, I can.

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Check out this explanation.


A simple way to think of it is think of the floor as a plane. Since 3 points define a plane, this is the min number of points needed to make a plane. Adding any more points may add instability (as those extra points may not be in the plane).

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Well, actually, a three-legged stool will always be more stable (on a perfectly flat floor) than a four-legged stool, why, because it takes only three point to define a plane, and if that plane happens to be a flat floor and the three points happen to be the ends of the legs of a three-legged stool, the the stool will be stable. With four points (a four-legged stool), one of them could be outside of the plane and thus, contribute to instability of the stool.