I suspect that the reason may be that people mostly talk about speed in
regards to traveling over relatively long distances and intervals. Doesn't
everyone get the same math problems in school about the train traveling a
certain number of miles, etc.? If I'm planning to drive to LA and want to
figure out how long it takes, it's a lot easier to use mph or km/h. Who
expresses travel time in seconds, or distances in feet or meters? That
would be 20-25 ks for me, so if I leave at 8:00 a.m. I will get there, when?
How many feet are in 350 miles? I think that the majority of people most
often encounter speeds when traveling, so it's easier for them to think of
speed in these units, even when talking about wind velocity, etc.
Granted, in metric it's easy to convert between m and km, but does anybody,
anywhere, use only s and ks instead of hours and minutes? If we did, then
we'd know that m/s is the same as km/ks and this would feel more natural to
use, but the entire world is still using hms time, even with SI.
In the US, speeds are usually regulated in increments of 5 mph. (I have
seen one or two exceptions.) 1 m/s is about 2.237 mph, so here are some
rounded conversions:
MPH m/s km/h
5 2 8
10 4 16
15 7 24
20 9 32
25 11 40
30 13 48
35 16 56
40 18 64
45 20 72
50 22 80
55 25 89
60 27 97
65 29 105
70 31 113
75 34 121
It is not hard to imagine that if road speeds were to be expressed in m/s,
that a smaller number of 5 m/s increments would be used.
m/s MPH km/h
5 11 18
10 22 36
15 34 54
20 45 72
25 56 90
30 67 108
35 78 126
--
John Hynes
www.decimaltime.org
2006 Jan. 25.281 UT
----- Original Message -----
From: "Jon Saxton" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[email protected]>
Sent: Tuesday, January 24, 2006 8:36 PM
Subject: [USMA:35833] Re: Speed in km/h vs m/s (was Weatherbug)
Never mind how wind speed is measured. Why do we (i.e. the general
public) expect speed in mi/h or km/h? I find it easy to visualise 3 m/s
or 10 ft/s because I can mentally picture such a distance and imagine
something traversing that distance in one second. I cannot do the same
mental exercise to attach meaning to 9.6 km/h.
There has to be some historical reason for it.
Martin Vlietstra wrote:
My understanding is that meteorlogists measure wind speed in m/s, but
that
it is converted into km/h for the benefit of the general public. One
could
however consume many litres of beer discussing this one in a pub.
--
What do you think happens to mail addressed to "spam.trap"?
