 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Natural Science Forum / Physics / General Physics / August 2008a thought experiment
Imagine a very long, low friction surface, in outer space, i.e. gravityless. You press a steel ball against this table, and start it rolling. You then release the ball and table. Does the ball continue to roll along the surface? -- Rich > Imagine a very long, low friction surface, in outer space, i.e. > gravityless. [quoted text clipped - 3 lines] > > Does the ball continue to roll along the surface? Low friction... means there is friction which implies that the surface is not perfectly smooth... and no force to hold the ball to the surface. Conservation laws apply. > > Imagine a very long, low friction surface, in outer space, i.e. > > gravityless. [quoted text clipped - 9 lines] > > Conservation laws apply. --------------------- since you pressed it to the surface it will not stay attached to the surface it will .... surprise ...... roll but ....... will move (rolling) but further and further away from the surface !!! think about an elastic rubber or tennis ball you see the other guys know abstract rules but they dont notice the 'little details ' .....(as well) sometimes the devil is in some little details ..... ATB Y.Porat ------------------------------------- > Imagine a very long, low friction surface, in outer space, i.e. > gravityless. [quoted text clipped - 3 lines] > > Does the ball continue to roll along the surface? Momentum is conserved. Angular momentum is conserved. What would kick in to change its rolling? > -- > Rich In sci.physics, RichD <r_delaney2001@yahoo.com> wrote on Fri, 29 Aug 2008 21:16:05 -0700 (PDT) <c681255b-a8a9-42a1-ae9e-247617ff4cf5@e53g2000hsa.googlegroups.com>: > Imagine a very long, low friction surface, in outer space, i.e. > gravityless. [quoted text clipped - 6 lines] > -- > Rich Yes, the ball continues to "roll" along the surface. Since it is low friction both angular and linear momentum are conserved. In real life the ball will probably deviate from the table unless additional forces (e.g., magnetic) are involved, as no one can get the vectors exactly right, but it would continue to spin.  Signature#191, ewill3@earthlink.net Useless C++ Programming Idea #12995733: bool f(bool g, bool h) { if(g) h = true; else h = false; return h;} ** Posted from http://www.teranews.com ** On Aug 30, 2:35 pm, The Ghost In The Machine <ew...@sirius.tg00suus7038.net> wrote: > Yes, the ball continues to "roll" along the surface. Since it is > low friction both angular and linear momentum are conserved. > > In real life the ball will probably deviate from the table unless > additional forces (e.g., magnetic) are involved, as no one can > get the vectors exactly right, but it would continue to spin. Correct. probably depends on how precise the ball and ramp are constructed. You would have gravitation and Van der Waals forces holding the ball to the track but as these are very weak, the track would have to be absolutely flat and the ball absolutely round so as not to bounce the ball off the track as it continued forward and continued to turn. > On Aug 30, 2:35 pm, The Ghost In The Machine > [quoted text clipped - 12 lines] > not to bounce the ball off the track as it continued forward and > continued to turn. ---------------- it will certainly bounce of the track! because it was ** pressed to it ** at the beginning to the track dont you know that even a steel ball has some elasticity ?? or you need first to be a structural engineer ?? (:-) ATB Y.Porat -------------------------------- On Aug 30, The Ghost In The Machine <ew...@sirius.tg00suus7038.net> wrote: > > Imagine a very long, low friction surface, in outer space, i.e. > > gravityless. You press a steel ball against this table, and start [quoted text clipped - 8 lines] > additional forces (e.g., magnetic) are involved, as no one can > get the vectors exactly right, but it would continue to spin. That's part of the motivation for the question... on earth, there is gravity, constantly pressing the ball and track together. When that force disappears, does 'rolling' make sense? And what if the surface is frictionless? In the example, there would be gravitational attraction between ball and table, and surface imperfections opposing that, so it's tricky. Also, one must press the objects together initially, to start the roll; when they are released, there is decompression as they spring back to shape. So it seems they would separate immediately. -- Rich |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.