August 10, 2007: Stuck hummingbird

[SeanAhern]

Originally Posted by xoxoxoBruce

Tensile strength of steel means nothing but the resistance to breaking with a steady straight line pull. Any vector from that state, such as shearing, all bets are off.

True. But with a spider web, any force on it is going to turn into a tensile force pretty much immediately. To shear a spider web strand, you'd have to have some way to keep the strand pointed one direction while applying force in another. Since the strand is, for all intents and purposes, a 1-dimensional object, it's going to be pulled parallel to your force vector immediately and your force will become purely tensile.

Originally Posted by xoxoxoBruce

Also, in order to have a tensile pull, the thread must be firmly attached. In the case of spider webs, it would depend on glue being stronger than the web.

Now that's interesting. Given a force upon a single spider web strand, what is the material that holds it to the tree/brick/wall/branch that it's attached to? And what is that material's tensile strength? If it's knotted and twisted web strands, we're back to the tensile strength issue. If it's something else (glue?), we have a new set of possible failure modes.

Interestingly enough, there are types of steel that are stronger than spider web. Piano wire, for instance. See http://en.wikipedia.org/wiki/Tensile...sile_strengths.

[xoxoxoBruce]

Originally Posted by SeanAhern

True. But with a spider web, any force on it is going to turn into a tensile force pretty much immediately. To shear a spider web strand, you'd have to have some way to keep the strand pointed one direction while applying force in another. Since the strand is, for all intents and purposes, a 1-dimensional object, it's going to be pulled parallel to your force vector immediately and your force will become purely tensile.

Yes, but we weren't talking about the pictures. Sarasvati48 was questioning my statement;

I'd guess that if the Hummer was outside it would easily fly through a web. But hovering up against the skylight, with no momentum, it just got more tangled and more tired.