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Rotations Per Minute Needed to Balance a Top 
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#1
Jul3114, 09:48 PM

P: 19

I have little to no experience with this area of physics, so don't assume I know certain things. A cone is spun (with the tip down) at a constant, not decreasing, RPM (Rotations per Minute). What is the minimum RPM for it to stay there without falling, and (if possible) the minimum RPM necessary to make it seem as thought it might be stationary? If dimensions are needed, I would not be able to give them, but I can give ratios, or I can put it in units that have no real world value.



#2
Jul3114, 10:50 PM

P: 3

If we aren't considering other realworld factors, the cone could balance without rotating at all.



#3
Jul3114, 11:04 PM

P: 19




#4
Jul3114, 11:23 PM

P: 3

Rotations Per Minute Needed to Balance a Top
Making the cone "seem as though it might be stationary" is just a matter of properly aligning the center of mass and the angle of rotation.
If we're ignoring friction, what forces are you imagining would make our cone fall over, at any RPM? Unsure what "realistically" has to do with a scenario where we are ignoring friction. 


#5
Jul3114, 11:30 PM

P: 19




#6
Jul3114, 11:42 PM

P: 3

Further, in order to "appear stationary," by which I assume you mean no procession (wobble), the top would need to be spinning in this balanced position anyhow. If the top was spinning from any other position, there would also be some wobble/procession, although the amount of wobble is inversely proportional to the rate of rotation. (That is, the faster we spin the cone, the less noticeable the wobble will be, but it will still wobble if it wasn't balanced.) 


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