Accelerometer

The pedants are getting faster

Sir, Us Anoraks have a reputation for being boring and getting up people's noses. My Daddy said that most families don't have a reputation of any sort so we should be proud of ours and should strive to maintain it.

Crateagus set us a crossword clue; 'it measures an aircraft's increase in speed', to which the answer given was 'accelerometer'. Through your columns, as politely as possible and in Rhyme, I pointed out that an. accelerometer does not measure 'increase in speed' but rather, 'the rate of increase in speed'. (In an aircraft it is this quantity that is so important since it determines the stresses imposed on the structure, it determines the so called 'g' loading. More strictly, in Physics, acceleration is the rate of increase in velocity, but I won't bore you even further with the distinction between speed and velocity).

Now Crateagus tells the world, or your readers anyway, that he was right and am wrong! Me an Anorak and a spotter! It just won't do.

My Dictionary says (and anyone can tell just from the word itself) that an accelerometer measures acceleration. If Crateagus is right then 'acceleration' means 'increase in speed'.

Let us suppose that an aircraft increases its speed from 300mph to 400mph. The increase in speed is 100mph and, according to Crateagus, that is what the accelerometer would indicate (and, according to him, the acceleration is 100mph). If, however, it took an hour to achieve this increase any schoolboy would agree that the acceleration was relatively low. If, on the other hand, it achieved this increase in just 2 seconds, surely we would all agree that that would be a fairly brisk acceleration. Clearly the 'acceleration' depends not only on the increase in speed but also on the time taken to achieve that increase. (In the first case the acceleration would have been 100mph/hour, or 0.0012g and in the second case it would have been 180,000mph/hour, or 2.27g), According to Crateagus, however, the acceleration was the same in both cases. What nonsense!

Chambers Dictionary may admit a broad interpretation of 'acceleration' as 'increase in speed' but an accelerometer quite definitely measures 'the rate of increase of speed'. If I find that Chambers says differently, as Crateagus claims, I will inform them of their error.

By the way, Crateagus suggested that I should go to Pictionary ( I couldn't find where it is situated) but I would suggest that it is he who should go there, not I.

I hope that you have been thoroughly bored by this letter and will allow me thoroughly bore your readers. My Daddy would be pleased.

A.N. Anorak