If our legs bent in the opposite direction, then how would the chair be shaped?
965900
Actually, I doubt we'd sit at all.  I'm looking at my parrot, and she has knees that bend backwards.  She just bends her knees on her perch, and when she sleeps she lifts one leg up and tucks it under herself.  I think we'd have a modified perch instead of a chair, and "sit" by getting into a reverse crouching position, just like a bird.
494278
a trapezoid.\n   __\n  /__&#92;
1069501
I have scoliosis, so my spine is curved in a backwards "S" shape. I wish so much that it were perfectly straight. It would make me about 3 inches taller and have less back problems.\n\nLuckily mine isn't so bad that you can see it when I'm wearing my clothes, but it's pretty obvious when I'm not. I wish I could say something superficial here like having bigger breasts, but if I only have one wish, it would be the straighter back!!
981770
Its movements would depend entirely on joints on the limbs, like most robots. It would be more difficult to share the body's weight and vertical acceleration loads among the limbs. and without spinal flexibility the impact loads would be much worse. Different gaits (e.g., a horse's walk, canter, trot and gallop) would be difficult since spine motion can assist in implementing fore-and-aft limb motion differences.
760426
Figure out the centripetal force.  After that, this becomes a sliding problem turned on its side.
854369
More stable. Imagine hanging a lantern upside down.
1063262
there would be nothing left of the chair. first of all atoms can neither be created nor be destroyed.therefore u can't take atoms of a chair. molecules can be taken off and nothing woud be left as MATTER IS MADE OF MOLECULES.
250305
Lunges and reverse leg raises, also try side leg raises on the floor to give a more round shape
79452
If you lay it out, it has a 'T' shape. (The sleeves to the body)
123300
i would say, based on the human body being symetrical, if we only had one hand, it would have to be in the middle of our chest. that could be dangerous i think.
520200
assumeing that one leg wasnt longer than the other, and that you couldnt fly and just walk straight out into space, you WOULDNT end up back where you started if walking in a straight line, because the earth isnt perfectly round...  you would have to walk east-west on the equator only
578743
Ok, I would normally be ofended by such questions, but there is a perfectly logical answer: Lets see you swing that club with a couple melons hanging inside your shirt. Seriously. Try it. It's incredibly hard. We need to bend out knees and arch our backs in a totally different way, just to get our arms straight.
359268
tja... depends on which direction your hips bend - the knees are only one half of the equation! ;)\n\nAssuming your hips bend backwards, your butt would be in front of you, and this means a chair would look exactly the same way, becuase your knees would bend backwards. But the back of the chair would now be in front of you.
1177142
Good point. If an intelligent designer existed I think we would have a ribcage all the way down to our waist. An extremely flexible one that's also bulletproof.
192657
No way to know.  What is the shape of "everything"?  I think it is round and that if you go to one end, you'll end up back at the same point if you keep going the same direction.\n\nGood question.
459581
Your question is unclear about what set of assumptions you want to use. You seem to imply a perfectly constructed stool, with a perfectly centered force, using incompressible material. You want the stool to have no mass, and you imply that you want to use statics to solve this problem. Strictly applying statics, this system is indeterminate, NOT the ridiculous answer of 0 [N] in two legs and W/2 [N] in the others. There are only 3 equations of equilibrium here, 1 for vertical forces and 2 for moments. Since you have four legs, this system cannot be solved by statics alone. Treating the stool as a deformable structure, you can use geometric compatibility to get a fourth equation. I challenge you to find a competently built stool that has 0 [N] in any leg (a physical stool built of real materials), or an incompetently built stool with 0 [N] in any two legs (unstable system that is obviously not static). The answer indicated as "correct" requires an incorrect application of statics. A large part of studying physics is learning when to use a particular tool, and the physical limits of that tool.\n\nedit: \nI am perfectly aware of what a zero force member is, and there are no zero force members here. You can only find zero force by statics if the structure is determinate, which is not true in this case.\n\nI completely agree with the PowerPoint presentation (definitely not a proof BTW). "But if one leg does not touch the floor, the force in it is zero. If one leg is zero, then the opposite leg is also zero by moment equilibrium. The two remaining legs carry all of the load = 90 pounds/leg. All four legs must be designed to carry the 90 pounds (since any two legs could be loaded)." only applies if the premise is satisfied, namely "if one leg does not touch the floor". I assure you, the normal idea of a four-legged stool requires all four legs to touch. Notice they finish off the calculation using a 45 lb/leg design load, not 90 lb/leg.\n\nI did not call you ridiculous; I rarely resort to name-calling. Please use the built-in spell checker.
162135
yes, how would feel if the table was reverse?