What causes a CD to appear to float on a glass surface?

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Discussion Overview

The discussion explores the phenomenon of a CD appearing to float on a glass surface, examining the forces at play and the role of surface interactions. Participants consider various explanations, including the effects of air pressure and surface smoothness.

Discussion Character

  • Exploratory
  • Conceptual clarification

Main Points Raised

  • One participant notes that the CD seems to float due to a vacuum between it and the glass, prompting a request for clarification on other possible forces.
  • Another participant suggests that the clear coating on the CD separates the actual layer from the air, although the relevance of this point is questioned.
  • A different participant argues that the apparent floating is due to air being trapped between the smooth surfaces, which creates pressure that makes the CD seem to stick to the glass.
  • One participant expresses a feeling of overthinking the question after receiving feedback.

Areas of Agreement / Disagreement

Participants present multiple views on the explanation for the CD's behavior, with no consensus reached on the primary cause. The discussion remains unresolved regarding the exact forces at play.

Contextual Notes

There are assumptions about the smoothness of the surfaces and the role of air pressure that are not fully explored. The discussion does not clarify the extent to which the coating on the CD affects the interaction with the glass.

loststylez
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I know the question sounds a little bit noobish but If you place a CD on a clean glass table seems like the CD is floating. There's vacuum between the CD and the glass stopping you from picking it up yet the CD seems to be floating.
If not I would like to know what other forces could be acting there.
 
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loststylez said:
I know the question sounds a little bit noobish but If you place a CD on a clean glass table seems like the CD is floating. There's vacuum between the CD and the glass stopping you from picking it up yet the CD seems to be floating.
If not I would like to know what other forces could be acting there.

Er... you do know that there's a clear coating on the CD that separates the actual layer from air, don't you?

Zz.
 
I know (I'm a computer geek).. but how's that relevant to the question ?.. except for the fact that it's a near-perfect plane that could enforce my question.
 
There's vacuum between the CD and the glass stopping you from picking it up yet the CD seems to be floating.
If not I would like to know what other forces could be acting there

That's just air being caught between the smooth, very flat surfaces. Since the separation is narrow, the air can only escape (or enter) slowly, and the resulting pressure causes it to seem to float (or 'stick'). The air escapes after a few moments and the CD touches the glass.
 
Thanks, I guess I was thinking too far !
 

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