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A PHYSICIST WRITES . . .

(July 2011)

I must start this column by recording a Ďmilestoneí: in May, my Toyota Corolla clocked up 100,000 miles. At least, thatís what the odometer showed ... as I said some years ago (recalling when my previous Nissan Sunny had performed the same eye-catching trick), the accuracy of a carís distance-measuring system is probably no better than one in a hundred, at a guess. This means that the 100,000 was possibly wrong by 500 miles either way.

Even so, as we arrived home after a day out, it was quite satisfying to see all the digits change at once, just as we entered the driveway. OK, I admit I had to drive round the houses for a bit, in order to engineer this. And then I felt I wanted to leave the car sitting there for as long as possible (in spite of my needing it for another trip out), restored to showroom quality in one respect at least, namely the displayed row of all zeros ó if you overlooked the 1.

I bought my Corolla just ten years ago (with 29K on the clock). Iíve mentioned various features of it over the years but not, I think, its alarm system. This is probably nothing unusual: to set the alarm you press the lock button on the remote once (and then once again if youíve left windows open and you donít want the wind to set the siren off).

Every so often I go straight to the boot with the key, forgetting to press the unlock button first, and inevitably the alarm goes off. I used to look around, because the noise didnít seem to be coming from my car! The reason (I realized later) is that the siren is hidden at the front of it.

Then one day, having again opened the boot first, I noticed that the alarm hadnít gone off, nor indeed had I heard it for quite a while. A quick test confirmed that although the locking action and hazard lights were working, the siren wasnít. It took me much longer to locate it ó well, you wouldnít expect it to be easy to find (especially when silent). And extracting it was quite impossible, so I had to give the garage the job of replacing it. Anyway, my advice would be to test your carís alarm occasionally like I do, otherwise if it fails you will never know.

This leads me on to another surprising problem Iíve faced: if you press the unlock button but then donít open a door (or the boot) within 30 seconds, the car automatically locks again, leaving the alarm activated. This is obviously a built-in safeguard against pressing the button unintentionally without realizing. And itís nothing to worry about ... until you have trouble with one of the press-switches on the door-frames that keep the interior light on when a door is open. The alarm system (in my car, anyway) relies on these switches to tell it that you have boarded the car!

In this case it was the switch on the passenger side that got gummed up. So you can guess how rarely it was that the car did lock up again automatically (with passenger inside) just as I was about to get in myself. And how long it took me to work out why this was happening at all.

Now to return to a topic that isnít really connected with motoring. In February I asked a question that displayed my ignorance about weather systems: simple physics (my preferred sort) says that winds ought to blow straight from high-pressure regions to low ó so how is it that they always travel around the Highs and the Lows? Actually I did have a rather foggy idea of the reason, but I was pleased to receive an explanation from a group member.

The key to the mystery is the rotation of the earth: letís suppose a wind (at our latitude) is trying to blow northwards, from high to low pressure. Because the High (further south) is being carried round the earth faster than the Low (further north) is, the wind ends up missing both of them, going clockwise round the High and anticlockwise round the Low ... are you convinced?

Hang on: there is a connection with motoring! If you are speeding round a left-hand bend, and your child H in the seat behind you aims a missile accurately at child L on the passenger side, it should just miss for the same reason, namely that H is being carried round the curve faster than L is. Does this clarify the wind picture?

I know I risk losing readers by bringing in too much physics when Iím trying to elucidate a phenomenom. So in my remaining page-space let me introduce a Ďnewí concept by using a simple item as a first example: a long lever, with a pivot near one end.

By pushing at the far end, you can lift a large weight near the pivot. Or by moving the pivot end, you can shift the other end a large distance. Either way, something is being greatly amplified, and for me, amplification is an idea that runs in many directions through physics and much else besides.

Examples in your car are the gearbox (when in low gear), power-steering, and hydraulic brakes ó all acting to increase the force applied. General examples are hi-fi amplifiers, broadcasting, the internet and the printing of newspapers (dare I mention too that this column is often read by up to a thousand advanced drivers, across several IAM groups).

And do you remember that I told you about a litter-picking movement I started last year, here in Earley? It now [October] has over 180 members, all going out regularly to keep their own streets tidy. One person, having spent his career carefully avoiding managing anyone, has now stirred 180 others into action: thatís quite some amplification!

[As of June 2014, our numbers are in excess of 260...]

Peter Soul

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