Tuesday, 28 August 2012

Pressure, friction and resistance


(28th August 2012 Signing on at 14:57)
I tried to do something today and I encountered resistance. As it happens I decided to avoid the resistance and do something entirely different which achieved another long term objective. The “thing” and the nature of the “resistance” are not that important, but it got me thinking about resistance in principle. Resistance in this case means resistance to change or to movement. Other similar words are “friction” and “inertia”, which imply a physical, or physics metaphor. Both “friction” and “inertia” will be felt at resistance to movement. You push against something and you can feel it pushing back. It doesn’t move. Friction and inertia are different though. Once you have got movement, then inertia will tend to continue the movement, whereas friction will bring the movement to an end.

Another possibility is that you are dealing with a mechanism which is jammed. Now this is a difficult problem, because from the outside, it is difficult to tell what the cause of the resistance is. If you apply sufficient force to a mechanism which is stiff with friction, then you will get it to move. If you apply increasing force to a mechanism which is jammed or seized then you may eventually cause movement but you may also break the mechanism.

This brings us on to the means of dealing with resistance. There are a number of techniques which can be used, either independently or in combination: the first and most obvious is the one already referred to, steadily increasing force; the second is shock, the classic “hit it with a hammer” (and maybe progressively bigger hammers!); then we have lubrication, adding oil to a mechanism or perhaps mounting an object on rollers; another approach is to “jiggle it”, if there is any movement at all, then “jiggling”, especially rhythmic jiggling, can create opportunities to  exploit both inertia and lubrication; a last  technique (or maybe rather a pair of techniques) is the application of hot and cold with a blowlamp or ice.

Let’s imagine specific cases where I have encountered resistance in the past. One which springs to mind is undoing nuts and bolts which have become seized with corrosion. In addition to the techniques for undoing them described above, I have also used destructive techniques to remove them. The destructive techniques I have used are: splitting the nut with either a nut-splitter or a chisel, cutting the head of the bolt off with a chisel, removing the head of the bolt or the nut by drilling it or grinding it, and of course, everyone’s  favourite; cutting the head of the bolt with an oxy-acetylene cutter! This last one is best suited to relatively large nuts and bolts in relatively exposed situations.

I’m not going to be able to write quite so much today. I have an task I have to start in about ten minutes time, so the “resistance” and the other things I have had to do today have rather got in the way. But this does not matter that much. I have still managed to make some progress with everything and that is something I find encouraging. If resistance does not bring things to a complete halt, then we must still be moving in the right direction. So long as we are moving in the right direction, we will get to the destination in the end providing the movement can be sustained for long enough,

And that made me thing of calculus and differentiation: distance travelled, velocity and acceleration. For a journey we should not expect to maintain the same velocity for the whole of the journey. An ideal journey would start off relatively slowly, accelerate to an efficient cruising velocity and then decelerate to come to rest at the destination. “Come to rest” that’s a nice phrase in the context. It has given me the idea of completing a journey and coming to rest. Most journeys are not ideal, they involve dealing with obstacles with reduce speed by introducing additional resistance and may even bring us to a standstill for a time. A real journey will have to deal with all sorts of things.       

 (Pages 1 plus, words 708, signing off at 15:28 ) 

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