Twisting a cork makes it easier to remove from a bottle
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Retrieved physics literature and online physics discussions indicate that adding a twisting motion during cork extraction helps overcome static friction, making the cork easier to remove from a bottle.
The stress field in a pulled cork and some subtle points in the semi-inverse method of nonlinear elasticity
In an attempt to describe cork-pulling, we model a cork as an incompressible rubber-like material and consider that it is subject to a helical shear deformation superimposed onto a shrink fit and a simple torsion. It turns out that this deformation field provides an insight into the possible appearance of secondary deformation fields for special classes of materials. We also find that these latent deformation fields are woken up by normal stress differences. We present some explicit examples based on the neo-Hookean, the generalized neo-Hookean and the Mooney-Rivlin forms of the strain-energy density. Using the simple exact solution found in the neo-Hookean case, we conjecture that it is advantageous to accompany the usual vertical axial force by a twisting moment, in order to extrude a cork from the neck of a bottle efficiently. Then we analyse departures from the neo-Hookean behaviour by exact and asymptotic analyses. In that process, we are able to give an elegant and analytic example of secondary (or latent) deformations in the framework of nonlinear elasticity.
# Why does twisting a cork make it easier to remove from a bottle?
Tags: newtonian-mechanics, forces, friction, everyday-life, free-body-diagram
- Score: 35
- Views: 7994
- Answers: 8
- Answered: yes
- Asked by: Larsa se eidaklaxtarsa (425 rep)
- Asked: 2021-07-26
- Edited: 2021-07-28
- Site: physics
## Question
When we want to remove a cork from a bottle first we turn the cork. Turning in one direction makes it easier to remove in the axial direction.
Does anyone know something more about this?
## Answers
### Answer by Steeven (score: 48)
When the cork is stuck and stationary, it is static friction which is culpable in keeping it fixed.
As soon as the cork moves - in any direction - the static friction is replaced by kinetic friction.
Kinetic friction, $f_k=\mu_k n$, is typically lower than the maximum static friction, $f_s\leq \mu_s n$ (because the kinetic friction coefficient typically is smaller than the static friction coefficient, $\mu_k<\mu_s$), and so, whenever you want to move something that is stuck, try to make it twist and turn and move before pulling it out.
With some downvoters and commentators bringing to my attention, that the answer above is not fully suffi
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