Who knows the meaning of 50 kilo picoh hours?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

04 January 2015

Measurement is an exact science. The symbols used for different units are very carefully selected to ensure that there is no mix-up. Nevertheless, there is at least one conflict that I am aware of.

The small letter “m” stands for metre and “s” is for second. However, “m” is also used as a prefix to mean “milli-”; that is one thousandth. So, when you write “ms”, it may confuse people because it is not clear whether you mean millisecond or metre second.

For that reason, a metre second is preferably written as “m.s”. But is it reasonable to expect such a unit of measurement? Isn’t “metre per second” the more common measurement?

Well, it is common to have two measurements multiplied together. The best example is the kilowatt hour used in measuring electricity consumption. Many people find it perplexing and they end up calling it kilowatt per hour.

It is kilowatt hour because it is obtained after multiplying the kilowatts of an electrical appliance by the time in hours that it has been operated. Since kilowatts are units of power and hours measure time, the result of multiplying the two is energy – this is what we buy from the electricity company.

The symbol for kilowatt hour is kWh. Notice that while the k and h are small letters, the W is capitalised. If you write KWH, that would be read as “kelvin watt henry”. The kelvin (written in small letters but symbol is a capital K) is a unit for measuring temperature while the henry (H) is for the inductance of a coil – that is, how well it induces voltage.

Therefore, as Martin Wyatt, my secondary school math teacher, used to say, KWH is “complete, utter, absolute, diabolical nonsense”! Another common symbol that would be categorised as the same kind of nonsense is “KMS”. It is often used to represent kilometres but in the science of measurements KMS means “kelvin mega siemens”. The correct symbol for kilometres is km – note that it does not have an “s” at the end.

Now, the National Transport and Safety Authority (NTSA) has erected road signs to indicate where the 50 kilometres per hour limit begin and end as required by law. Unfortunately, all the boards are wrong!

The road signs are written “50kph”. In the science of measurements, this means “50 kilo pico hours”. Kilo is, of course, one thousand; pico is the standard prefix to represent one trillionth, that is, 0.000000000001.

Now a trillionth multiplied by one thousand is a billionth. One billionth is called nano and its symbol is “n”. Therefore, instead of writing “kph” it would be much easier to write “nh” for “nano hour”.

But what does 50nh mean to a motorist? Absolutely nothing!

If NTSA had checked the highway code, they would have found that the standard speed limit sign has just a number written on it. Drivers are taught that the number is in kilometres per hour – km/h. After all, isn’t “km/h” what is written in the speedometer?