Were the Laws of Physics designed for torture?

[Vagulus]

Here is an issue to distract the scientific mind for a restful Festive Season.

This is a gumnut.

They fall from trees round here (Perth, Western Australia) by the tonne. They are quite small (about 9 mm in diameter) and the pointy end is sharp. You do not want to stand on the pointy end.

This is a pair of thongs.

You might call them flip-flops, jandals, japanese safety boots, whatever. They are popular footwear around here in the summer.

My problem is that when I am walking down the street, every now and then a gumnut jumps onto the sole of one of my thongs. It always lands round (flat) end down and pointy end up. This can be painful :( so I try to get rid of it. However, that is not easy. Shaking my foot attempting to dislodge the gumnut results in the gumnut snuggling further onto the sole of the thong, working its way steadily to lodge under the ball of my foot. This is extremely painful |[ It is also counter-intuitive.

My question is, what laws of physics (apart from Murphy's) decree that the gumnut will exhibit that behaviour?

 

[kuruman]

I am not sure that it's physics and not evolution. You see, it looks like the gumnut tree (?) has evolved so that people with thongs (or whatever) step on the gumnuts, walk away until they become painfully aware of them and discard them to plant another gumnut tree farther down the road.

 

[jedishrfu]

Perhaps it's evolutionary, by dropping this way the nut could be ideally placed to grow into a new tree. Gumnut trees with acorns weighted this way produced offspring with the same feature whereas gumnut trees who didn't didn't fare as well or at least they don't get stuck in your toes and so you don't notice them.

In any event, this will need further study. :-)

One solution, don't be that guy, wear shoes and avoid gumnut trees areas.

 

[Vagulus]

Whether it be evolutionary or creationary (in the 19th century, William Cowper wrote, "God moves in a mysterious ways; His wonders to perform ..." ) we must acknowledge the advantage to the species of tree in having its seeds spread far and wide. That, however, is a side issue. This moot is the way in which shaking the thong does not dislodge the gumnut from the upper surface of the thong but actually compounds the problem by moving the gumnut to a less probable and more painful position.

We know (thanks to Newton) that the gumnut cannot change its state of motion (stationary under the heel) without being acted on by an independent force. What force, then, acts towards the toes parallel to the linear axis of the foot such that the gumnut is moved from being under the heel to being under the ball of the foot?

 

[A.T.]

We know (thanks to Newton) that the gumnut cannot change its state of motion (stationary under the heel) without being acted on by an independent force.

This applies to inertial frames of reference, which the frame of the shoe is not during walking or shaking the foot.

 

[Vagulus]

That's why I am asking,

What force, then, acts towards the toes parallel to the linear axis of the foot such that the gumnut is moved from being under the heel to being under the ball of the foot?

We know the gumnut has Mass, and we know it moves. This must require a force (as far as I can work out). What is the force?

 

[sophiecentaur]

There are two possible Physics explanations. Aerodynamics and 'Statics'. The shape of the seed would make it end up in that orientation, I think, but I doubt that it is traveling fast enough for that to dominate. The more likely explanation is that the centre of mass of the nut is near the flat, wide side. So it will tend to reach a stable position with that side next to the ground. It's like one of those (more charming) wobbly toys that you cannot knock down. Any displacement from the upright position will involve raising the CM and that is what constitutes Stable Equilibrium.
But the design is smarter than just that. The pointy bit on the top is just an Evil bit of design which ensures it will be picked up in a thong / paw / hoof. As the seed rolls over the ground due to the sliding action of the foot, the point will eventually arrive at the top. Then it will stick into the sole. The clever bit of design is that the point is not too long and not too short so it is just right for your torture.
I suggest that a flame thrower, directed against the tree is the only solution.

 

[A.T.]

the gumnut is moved from being under the heel to being under the ball of the foot?

You lift the heel, the stuff rolls down forward and gets stuck between ball and shoe.

 

[anorlunda]

I think we have to look at how the gumout tree survived in the eons before homo evolved the thong appendage.

If trends continue, the thong will be replaced by the croc and the gumout seeds will have to adapt to a smaller size to fit through those holes.

 

[Vagulus]

There may well be something in this A.T.

You lift the heel, the stuff rolls down forward and gets stuck between ball and shoe.

I am thinking that the explanation might not involve directional force so much but instead be related to the gumnut moving to an area where it has greater freedom of movement, i.e. the gap between the instep and the thong which is greater than the gap between the heel and the thong. This theory, however, does not explain why the gumnut does not move to an area where it has even greater freedom of movement, i.e. the footpath. As sure as God made little apples (and little boys and other annoying articles) the gumnut will not readily leave the thong - I will have to remove the thong to shake it off.

How do we explain that?

BTW sophiecentaur, I don't know what your situation is but over here our friendly local tree-huggers would get very active if I took a flamethrower to the roadside trees in my suburb. Anyway, I like the shade.

 

[Dale]

How do we explain that?

I would guess it is mostly sampling bias. You tend to remember/notice the ones where it didn’t leave more than the ones where it did leave. More psychology than physics. A well designed experiment would need a method to address that issue.

 

[Vagulus]

So! It's all in the head!

We have had evolutionary, creationary, theological, and philosophical responses. This obviously has nothing to do with physics!

Merry Christmas Everyone