Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!know!news.cs.indiana.edu!news.nd.edu!liszt!przemek From: przemek@liszt.helios.nd.edu (Przemek Klosowski) Newsgroups: comp.arch Subject: Re: CD-ROM documents (was Paperless Office) Summary: constant angular velocity->linear velocity Keywords: CD ROM, read, velocity Message-ID: <1990Dec6.194458.1820@news.nd.edu> Date: 6 Dec 90 19:44:58 GMT References: <1990Dec5.105743.25693@actrix.gen.nz> <1990Dec6.154348.5206@d.cs.okstate.edu> Sender: news@news.nd.edu (USENET News System) Organization: University of Notre Dame, Notre Dame Lines: 26 In article <1990Dec6.154348.5206@d.cs.okstate.edu> norman@d.cs.okstate.edu (Norman Graham) writes: > >But suppose we reverse the situation and use a constant rotation speed >(i.e. constant angular velocity (CAV)). Then the distance between >transition A and transition B becomes a more complex problem. Remember >that because of CAV, the tangential velocity is increasing from >transition A to transition B (points on the inside of the disk are >spinning slower than points on the outside of the disk); thus we now >have acceleration to worry about. [I've not reasoned through this >(heck, it's just a USENET posting) but I believe the acceleration is >non-linear.] So, what _do_ we have to work with to determine the >distance between two transitions? Well, if the disk rotates at constant angular speed omega, the linear speed of a point at radius r is v = omega * r. The spiral is so tightly woven that for all practical purposes it can be treated as concentric (ie. the tangent to its direction is perpendicular to the radius). Even if it weren't, the Archimedes spiral would have some angle close to 90 deg (say 89.99 deg), and the linear velocity would be linear function of radius, too. The real problems may pop up when you consider excentricity of the tracks, but then they plague constant linear velocity scheme also. -- przemek klosowski (przemek@ndcva.cc.nd.edu) Physics Dept University of Notre Dame IN 46556 Brought to you by Super Global Mega Corp .com