sciman55 Posted June 14, 2005 Report Share Posted June 14, 2005 What would apply to acrobatics more; force, inertia and acceleration, or torque, moment of inertia and angular acceleration. Why? Quote Link to comment Share on other sites More sharing options...
Qfwfq Posted June 14, 2005 Report Share Posted June 14, 2005 Each one of these applies more than each of the others! Quote Link to comment Share on other sites More sharing options...
sciman55 Posted June 14, 2005 Author Report Share Posted June 14, 2005 I meant which of these would better apply to twists, somersaults and rolls and why? Quote Link to comment Share on other sites More sharing options...
Erasmus00 Posted June 14, 2005 Report Share Posted June 14, 2005 What would apply to acrobatics more; force, inertia and acceleration, or torque, moment of inertia and angular acceleration. Why? The answer is that both sets of terms matter equally. Acrobatics involves both center of mass motion (force,inertia, and acceleration) as well as rotation (torque,moment of inertia, and angular acceleration). Acrobatics jump as well as twirl, so only by applying both terms can such motion be analyzed. -Will Quote Link to comment Share on other sites More sharing options...
Qfwfq Posted June 15, 2005 Report Share Posted June 15, 2005 I meant which of these would better apply to twists, somersaults and rolls and why?In this case, torque etc. are more relevant because you're concerned with rotation. Quote Link to comment Share on other sites More sharing options...
sciman55 Posted June 15, 2005 Author Report Share Posted June 15, 2005 And how does rotation apply to everything? And in acrobatics what exactly does twist and turn mean? Quote Link to comment Share on other sites More sharing options...
Erasmus00 Posted June 16, 2005 Report Share Posted June 16, 2005 And how does rotation apply to everything? And in acrobatics what exactly does twist and turn mean? I'm not an acrobatics expert, but anytime you have something thats rotating, i.e. spinning on some axis, you need torque and the like to analyze whats going on. With linear motion, you need force, momentum, etc. In a cartwheel, a persons center of mass moves, which can be analyzed with frictional forces between hands and the ground or feet and the ground and the person spins around an axis roughly at its center, which can be analyzed with torques from these friction forces. -Will Quote Link to comment Share on other sites More sharing options...
zadojla Posted June 17, 2005 Report Share Posted June 17, 2005 The analyses would be difficult also because you could not treat an acrobat as an ideal particle, which is the basis for the simplicity of elementary physics. Acrobats perform some of their motions by changing the moment of inertia of some parts of their bodies relative to other parts.For a simple example, think of a cat twisting in the air to land on its feet. First it extends its back legs and curls up its front legs. This gives the front of its body a lower moment, so it can be twisted around to face the ground. Then it extends its front legs and curls up its back legs, so its front half has a higher moment, and brings the rest of its body around so it is upright, and able to land on its feet. A cat can do all of that in the time it takes to fall one meter. Quote Link to comment Share on other sites More sharing options...
Boerseun Posted June 17, 2005 Report Share Posted June 17, 2005 ... A cat can do all of that in the time it takes to fall one meter.Until you tie a piece of buttered toast to it's back, butter-side up.The catwill fall, to be sure, but just above the ground, the toast-effect takes over, whereby the inconsistencies below makes for an interesting effect: 1) A cat always lands on its feet2) Toast always falls buttered-side down The nett effect is that the cat will hover in the air, slowly turning around and around as either the toast- or cat-force comes closer to the ground due to the cat's wriggling. Quote Link to comment Share on other sites More sharing options...
Qfwfq Posted June 17, 2005 Report Share Posted June 17, 2005 Cats are not exempt from Murphy, so the toast will definitely prevail. Quote Link to comment Share on other sites More sharing options...
Boerseun Posted June 17, 2005 Report Share Posted June 17, 2005 You're probably right about Murphy. But - imagine the cat hawking up a hairball at the same time; wouldn't that propel the floating cat/toast combination backwards? It all depends wether the cat can keep its balance so that the toast don't flip over and overcome the Murphy-effect. So this will be a hairball-powered pussy-toast balance flying catmobile. Maybe we should shave it first, for the airodynamics? We might get an extra knot or so out of it? Quote Link to comment Share on other sites More sharing options...
Qfwfq Posted June 17, 2005 Report Share Posted June 17, 2005 Maybe we should shave it first, for the airodynamics? We might get an extra knot or so out of it?Perhaps, but don't forget we're more concerned with rotations, so it's torque we need to control! A shaven cat could sure spin round and round mighty fast... Quote Link to comment Share on other sites More sharing options...
zadojla Posted June 18, 2005 Report Share Posted June 18, 2005 The nett effect is that the cat will hover in the air, slowly turning around and around as either the toast- or cat-force comes closer to the ground due to the cat's wriggling.Hmm...maybe we should move this to one of the perpetual motion threads. Quote Link to comment Share on other sites More sharing options...
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