Quote:

Actually in practice the top speed shown with a 1 second interval is not much different from the doppler reading (while surfing) which upadates every 1/10th of a second. . . within 0.5 mph (well that’s what we have found anyway)

A one second interval is fairly standard and gives a useful indication of what’s going on IMO.

I don’t doubt this is true for the extremely heavy boards that you ride, Roy, but for typical surfboards, speed and direction can change very quickly. Consider the example that I gave and apply it to a typical weight surfboard.

As a matter of fact heavy boards accelerate FASTER than light boards

Quote:

BTW there is no such thing as an ‘instantaneous’ speed. . . by definition an instant has no length, therefore there can be no distance travelled and no speed, only a position in time and space

Roy, Roy, Roy… I think you should crack open a calculus or physics book before posting such a silly statement. This is simply not true. Google it. Instantaneous velocity is defined as the time rate of change of distance as the distance becomes infinitely small. In otherwords, it is the velocity at an “instant” of time.

Very sorry but that is a rule of thumb which obscures, by way of definition, the meaning of ‘infinite’ and ‘instantaneous’. . . . that kind of thing is common in mathematics and physics.

I terms of pure conceptual or philosophical thought, infinity, or the infinite is EVERYTHING, and the opposite of the infinite is NOTHING

The problem is the difference between purely mathematical and purely logical thinking, and possibly there is no one correct answer.

The mathematical treatment of infinity leads to some strange contradictions, for example, if we say that infinitely small has a size which is greater than zero, then

(a) There is something smaller than infinitely small, i.e zero. . . this is a philosophical contradiction because there can be no limit to the smallness of infinitely small. . . and being bigger than something (i.e zero) is such a limit

(b) If infinitely small is greater than zero then it MUST have a size. . . if it has a size, that size can be halved . . . leading to the contradictory notion that infinitely small can be divided by two !. . . . naturally it can be objected that the size of the infintely small item cannot be defined because we haven’t ever finished making it smaller. . . . but this is a poor answer.

I realise that the mathematical treatment of the terms ‘infinitely small’ and ‘instantaneous’ is useful, and that my treatment of the terms is perhaps more in line with mystical thought or the philosophy of the Ancient Greeks. . . but the mathematical treatment is still contradictory in purely logical terms.

BTW there is no need to call me Roy Roy Roy. . . just the one will do

Cheers !

PS In practical terms if the 1/10th of a second reading is close to the 1 second interval reading it takes the stuffing out of your argument against the usefulness of the 1 second interval. . . In my opinion.

.