Question on contact pulling force.

[Some dude]

   As I am walking through the store, I find a pop tube toy. I fidget with it a little bit, pulling it, and pushing it back together and do a few experiments because why not. I pull it in a way where the force must curve to reach the other side to confirm that a forces prefer to, in fact, travel in straight lines, simple enough.

   However, one thing that did peak my curiosity was that the popping ‘chambers’ popped from the edge and creeped towards the middle. My initial hypothesis was the two pulling forces would meet in the middle to where they would cause the chambers to have most stress, and pop from the middle out.

   After this observation, I have a few new ideas for this that I would like fact checked: A pulling force is usually visualized as an arrow pointing towards an object being pulled with the object doing the pulled on the opposite side of the arrow, however I suspect the arrow is more a backwards push than what is described. The arrow points towards the pulling object, and moves away from it, passing through the object being pulled (A pull arrow goes away from the puller, pointing towards the puller, while a push arrow goes from the pusher, pointing towards the push-ee). 

   Continuing, when I pull from one side and only hold the other side for Newtons 3rd law of motion (Only friction holding it down), I’d hypothesized from the previous idea, the pulled side would pop first, with the other side popping ever so slightly after, but there was no delay. 

   My second (I’ll admit, very out there) hypothesis: A ‘ghost’ force travels from the initial pull, towards to the end point before the pull force begins, and the ghost force checks for any equilibrium interrupting process that would balance the pull. Once not found, it would create a substitute counter in the form of newtons 3rd law.

   As known that forces move the speed of sound, one would likely reply to this with saying, “Forces can be thought well by imagining a bunch of marbles attached by rubber bands…You know,” but I then bring back up the pop tube.

   In an empty space with a bunch of marbles connected by rubber bands, a push on one side would go straight to the other side with no push back. If you can imagine a gradient with red being the most pushed on areas, and green the least, the point of push and area near it would be red, the middle of the ball-band bunch would be yellowing as it approaches green, and the end would be greenest. With the pop tube, as stated before, the chambers popping start from both sides even without a physical push from the other side. Of course this is simply explained by newton’s 3rd, but going back to the gradient, both sides of the pop tube is red which in the previous example was green, with the middle being yellow as always.

   I apologize to whom I tortured by reading this unreasonably long post that was probably filled with many brain dead statements.

[swansont]

It’s more like springs than rubber bands; these represent the electrostatic force present in bonds. So they are there for pushing and pulling, and it does take some time for these to propagate through a material, as you note.

[swansont]

 

So I looked up what these are; they're like the bendy part of a bendy straw. You can imagine that the bent sections "give" a little when you pull or push on them, but the end section is connected to the more rigid part, so the central parts would just expand slightly under a pull, like a spring, but the ones at the edge can't do this, so they "pop" open. As a trend, not an absolute, because the manufacturing variations mean that each section might require more or less of a force to make it pop.