Applying Torque to rotating objects in 3d space
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From: Armence on 7 Aug 2010 23:48 Let's say I have an object in 3d space (we'll say it's a uniform sphere to keep things simple for now) with angular velocity rotating about an axis. Now, I apply some torque to that object for some amount of time. The axis of that torque is not parallel to that of the initial rotation. How can I calculate the new angular velocity and new axis?
From: Uncle Ben on 8 Aug 2010 00:54 On Aug 7, 11:48 pm, Armence <arme...(a)gmail.com> wrote: > Let's say I have an object in 3d space (we'll say it's a uniform > sphere to keep things simple for now) with angular velocity rotating > about an axis. Now, I apply some torque to that object for some amount > of time. The axis of that torque is not parallel to that of the > initial rotation. How can I calculate the new angular velocity and new > axis? That's not a simple problem. Consider the earth, for example. The moon exerts a slight torque on it because the earth bulges a bit at the equator. The detailed result is quite complicated if you want detail, with precession and nutation. People have written whole books about the motion. I would start with Wikipedia. Uncle Ben
From: Armence on 8 Aug 2010 01:30 On Aug 7, 9:54 pm, Uncle Ben <b...(a)greenba.com> wrote: > On Aug 7, 11:48 pm, Armence <arme...(a)gmail.com> wrote: > > > Let's say I have an object in 3d space (we'll say it's a uniform > > sphere to keep things simple for now) with angular velocity rotating > > about an axis. Now, I apply some torque to that object for some amount > > of time. The axis of that torque is not parallel to that of the > > initial rotation. How can I calculate the new angular velocity and new > > axis? > > That's not a simple problem. Consider the earth, for example. The > moon exerts a slight torque on it because the earth bulges a bit at > the equator. The detailed result is quite complicated if you want > detail, withprecession andnutation > > nutation. People have written whole books > about the motion. > > I would start with Wikipedia. > > Uncle Ben Yes, I agree, this is a complex problem and unfortunately, wikipedia is not helping me much. The encyclopedic style is quite helpful for problems with which I am somewhat familiar but this is quite new to me. What would be the simplest version of the problem I described? It seems as though a sphere with initial angular velocity to which torque is applied once for some period of time. (or perhaps some angular acceleration instead of torque to keep things simpler) We can forget about the cause of the torque. I am imagining something like a spherical spaceship with weightless thrusters placed tangentially to the sphere. How would that problem look? Are there further simplifications that are necessary?
From: Androcles on 8 Aug 2010 01:38 "Uncle Ben" <ben(a)greenba.com> wrote in message news:e6bffe42-d249-4ee6-8dfa-28733d1699f4(a)x21g2000yqa.googlegroups.com... On Aug 7, 11:48 pm, Armence <arme...(a)gmail.com> wrote: > Let's say I have an object in 3d space (we'll say it's a uniform > sphere to keep things simple for now) with angular velocity rotating > about an axis. Now, I apply some torque to that object for some amount > of time. The axis of that torque is not parallel to that of the > initial rotation. How can I calculate the new angular velocity and new > axis? That's not a simple problem. Consider the earth, for example. The moon exerts a slight torque on it because the earth bulges a bit at the equator. ================================================== Bwahahahahaha! Bonehead's dog bulges a bit at the equator not because it ate Bonehead's sausages, but because Bonehead put a torque on its leash.
From: Androcles on 8 Aug 2010 03:10
"Armence" <armence(a)gmail.com> wrote in message news:84bc9575-3a60-4337-aa81-964846a61905(a)g21g2000prn.googlegroups.com... On Aug 7, 9:54 pm, Uncle Ben <b...(a)greenba.com> wrote: > On Aug 7, 11:48 pm, Armence <arme...(a)gmail.com> wrote: > > > Let's say I have an object in 3d space (we'll say it's a uniform > > sphere to keep things simple for now) with angular velocity rotating > > about an axis. Now, I apply some torque to that object for some amount > > of time. The axis of that torque is not parallel to that of the > > initial rotation. How can I calculate the new angular velocity and new > > axis? > > That's not a simple problem. Consider the earth, for example. The > moon exerts a slight torque on it because the earth bulges a bit at > the equator. The detailed result is quite complicated if you want > detail, withprecession andnutation > > nutation. People have written whole books > about the motion. > > I would start with Wikipedia. > > Uncle Ben Yes, I agree, this is a complex problem and unfortunately, wikipedia is not helping me much. The encyclopedic style is quite helpful for problems with which I am somewhat familiar but this is quite new to me. What would be the simplest version of the problem I described? It seems as though a sphere with initial angular velocity to which torque is applied once for some period of time. (or perhaps some angular acceleration instead of torque to keep things simpler) We can forget about the cause of the torque. I am imagining something like a spherical spaceship with weightless thrusters placed tangentially to the sphere. How would that problem look? Are there further simplifications that are necessary? ============================================== You want to program this shuttle's computer, huh? http://www.youtube.com/watch?v=q3oHmVhviO8 In the real world autopilots have been doing it for years, but as I understand it the real shuttle no longer docks with the ISS. Apparently it was scrapped way back in 2010. I'm not sure if a spherical shuttle would be much use for reentry. The British Harrier has weightless thrusters on the wing tips. http://www.youtube.com/watch?v=-kDb99ftPlY It's all about rotation and translation. Get Uncle Bonehead to explain the difference between relative velocity and closing velocity for you since he claims to know what it is; he'll tell you to start with wackypedia. Bonehead still lives in 1905 sci-fi. |