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that has nagged me for decades. Perhaps someone can clarify.=0A>>>>=0A& This is a multi-part message in MIME format. ------=_NextPart_000_0099_01CD98FF.5F28E350 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Patrick & All, Sept 22, 2012 Thanks for the detailed explanation. I have read this several times = and will give it further study. We agree that mass, by definition, will = be independent of the setting and that weight will vary depending upon = gravity.=20 But even the determinations of mass on an equal-beam balance will be = influenced by ambient gas pressure unless the reference mass and the = unknown mass have equal volume. And a beam balance will register noise = (I expect) at zero gravity. Going to the moon to test this is expensive and, in any case, one = would need permission of the owners. It is more convenient to consult a = Quantitative Chemistry text. If the unknown object is not as dense as = the reference, then 'mass' of the unknown will appear to increase when = gas is removed from the balance. And my Quantitative Chem. text states = that "Thus the mass of the object in vacuum is greater than that = measured in air..." But, on the other hand, if the unknown is more dense than the = reference then 'mass' of the unknown will appear to have decreased when = gas is removed. Wow we have just created and destroyed matter with a = vacuum pump.=20 It gets much worse if you use a weighing system in which no = reference 'mass' is concurrently used, e.g. a spring scale calibrated on = earth using a series of references 'masses'. The mass will appear to be = much less on the moon and become zero at zero gravity. Therefore, even an equal-beam balance does not really measure mass. = It is responding to F which is equal to mg, the two arms being in = balance when the reference F, by nature of the equipment design, applies = an upward force F that equals the downward F of the unknown when the two = are in balance. I suspect that the different conventions over time reflect different = contexts. If you dealt with objects at rest (e.g. preparation of = reagents) then weight would be standard usage (sometimes called mass to = appear learned). If you dealt with objects in motion then mass would be = standard.=20 Units are only as good as they are useful. I notice that spring = scales are now calibrated in Newtons. How would one check that = calibration ? With a box of standard Newton Forces ? =20 It will just take a while and probably a fresh set of participants = to make the adjustment.=20 I still buy apples by the pound but to prepare for the changeover; a = Newton of apples will be one apple. Right ? Yt, Dave Webster, Kentville =20 ----- Original Message -----=20 From: Patrick Kelly=20 To: naturens@chebucto.ns.ca=20 Sent: Saturday, September 22, 2012 11:28 AM Subject: Re: [NatureNS] Correction; Fw: Velocity of light I'm not sure I see the confusion arises over the kg being a unit of = mass. I just covered this in my last astronomy class and why people use = the words mass and weight interchangeably when they are two totally = different things. Mass is a measure of how much matter an object = contains. You measure mass with a scale. A 1 kg bag of sugar has the = same mass here as well as on the Moon, as on a scale you would still = need a 1kg mass to balance it. Weight is a force, not a measure of mass. The problem is not helped = when people still use the English unit of "pound" for both weight and = mass. The English system unit of mass is the slug, not the pound. Your = weight is the force of gravity acting on your mass and depends on your = mass, the mass of the Earth and the radius of the Earth. if you are = standing on the Moon (different mass and radius) you will "weigh" less = because the gravitational force is less. If you stood on a doctor's = scale on the Moon you would find that your mass is the same as it is on = Earth. In the metric system, the unit of force is the Newton (the symbol is = N). 1 N is the force that is required to accelerate a 1 kg mass at the = rate of 1 m/s/s. (i.e. Force =3D mass X acceleration).=20 At the surface of the Earth, the gravitational force =3D G x m x M / = (r x r), where G is the gravitational constant, m is the mass of a small = object (like a person), M is the mass of the Earth and r is the radius = of the Earth. If you drop that small object, this force will also produce an = acceleration (because Force =3D mass X acceleration). So F =3D m x a. = Since the force comes from gravity: m x a =3D G x m x M / (r x r) Note that since the small object is on both sides of the equation, you = can cancel it, and thus you get: a =3D G x M / (r x r) This acceleration gets a special symbol, g, and has a value of 9.8 = m/s/s (which you can round of to 10 m/s/s). This is the rate at which = all objects at the surface will fall (in a vacuum). If you go to the = Moon, since M and r are different the surface gravity there is much = lower, 1.7 m/s/s of about 1/5 that of the Earth. You can also use the surface gravity as a quick way to calculate your = "weight" by multiplying your mass (in kg) by g. A 1 kg mass has a = "weight" of 9.8 N and a person such as myself with a mass of about 100 = kg would have a weight of 980 N. Thus a proper metric scale would NOT be = graduated in kg, but in Newtons. I expect there are two reasons they = don't. One is that most people would freak if their "weight" appeared to = be 10 times what they thought it was, and secondly, since they assume = you are using the scale at the Earth's surface, they have "converted" = the force back into "mass". Just don't take it to the Moon and expect it = to work properly! Pat PS: For those who are curious, a mass of 1 slug has a weight at the = Earth's surface of 32 pounds. The kg a unit oef mass=20 On Sep 22, 2012, at 9:58 AM, David & Alison Webster wrote: Hi Fred & All, Sept 22, 2012 Explanations of weight/mass usually resemble inconsistent = confessions obtained by torture but I guess that is ok now. It seems logical to me that weight should be treated as a special = case of F=3Dma where a in this case is g and F is measured by exerting = an equal and opposite force upward to keep the mass from falling. One could then determine the magnitude of mass as F/g and then = proceed to work out units of momentum, inertia etc from there. But unfortunately kg has been defined (or perhaps redefined) as a = unit of mass which leads to everything being a hopeless muddle. I would try to reform the system of units dealing with weight, = mass and distance but I am tied up this afternoon. Yt, Dave Webster, Kentville ----- Original Message ----- From: "Fred Schueler" <bckcdb@istar.ca> To: <naturens@chebucto.ns.ca> Sent: Friday, September 21, 2012 9:19 PM Subject: Re: [NatureNS] Correction; Fw: Velocity of light Quoting David & Alison Webster <dwebster@glinx.com>: I just dug out my 1st yr Physics (Weber, White & Manning, 1952) = and they consistently refer to 'speed of light' as opposed to 'velocity = of light'. Four other sources (1941, 1948, ~1965 &1962) have velocity. * indeed, it would be ineffective to purge society, or even = literature, of all who misuse speed/velocity or weight/mass. Or, to = bring it closer to natural history, all who refer to nonhemipterans as = "bugs." fred. = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D ----- Original Message ----- From: "David & Alison Webster" = <dwebster@glinx.com> To: <NatureNS@chebucto.ns.ca> Sent: Friday, September 21, 2012 7:44 PM Subject: Velocity of light Dear All, Sept 21, 2012 The recent discussion about transmission of electricity, = reading of HEAT and reading some of Energy... brings to the forefront a = question that has nagged me for decades. Perhaps someone can clarify. In the typical elementary physics text we are told that = velocity is a vector quantity, and to quote one text "velocity... may = be defined as the rate of change of position in a given direction". = But "In cases where the direction of motion does not require to be = considered , the term speed is employed to express the rate of = travelling." Based on the above I would think that the rate of movement of = light should be called speed, i.e. speed of light but I think it is = always called velocity. For example, if light from the sun is reflected from two 45o = mirrors then a beam of light could be directed from the earth back to = the sun and, the velocity would then be minus 3 x 10^10 cm/sec. Or if = variously scattered or reflected then the velocity, relative to the = initial sun to earth direction, would always be less than 3 X 10^10 and = after several reflections might be zero. Is there some good reason why the speed of light is termed = velocity of light ? Or is it called velocity because the textbook = authors forget what they said in chapter one by the time they write = chaper eleven ? (And they all copy from each other) Yt, Dave Webster, Kentville ------------------------------------------------------------ Frederick W. Schueler & Aleta Karstad Bishops Mills Natural History Centre - = http://pinicola.ca/bmnhc.htm Mudpuppy Night in Oxford Mills - http://pinicola.ca/mudpup1.htm Daily Paintings - http://karstaddailypaintings.blogspot.com/ South Nation Basin Art & Science Book http://pinicola.ca/books/SNR_book.htm RR#2 Bishops Mills, Ontario, Canada K0G 1T0 presently in Cochrane - 49.06274N 81.02415W - on the great Ontario Claybelt (613)299-3107 <bckcdb at istar.ca> http://pinicola.ca/ ------------------------------------------------------------ ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2221 / Virus Database: 2441/5278 - Release Date: = 09/19/12 = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Patrick Kelly Director of Computer Facilities = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Faculty of Architecture and Planning Dalhousie University = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D MAIL COURIER PO Box 15000 5410 Spring Garden Road Halifax, Nova Scotia B3H 4R2 Halifax, Nova Scotia Canada Canada = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Phone:(902) 494-3294 FAX:(902) 423-6672 = E-mail:patrick.kelly@dal.ca = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2221 / Virus Database: 2441/5278 - Release Date: = 09/19/12 ------=_NextPart_000_0099_01CD98FF.5F28E350 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content=3D"text/html; charset=3Diso-8859-1" = http-equiv=3DContent-Type> <META name=3DGENERATOR content=3D"MSHTML 8.00.6001.19298"> <STYLE></STYLE> </HEAD> <BODY=20 style=3D"WORD-WRAP: break-word; -webkit-nbsp-mode: space; = -webkit-line-break: after-white-space"=20 bgColor=3D#ffffff> <DIV><FONT size=3D2>Hi Patrick & All, = =20 Sept 22,=20 2012</FONT></DIV> <DIV><FONT size=3D2> Thanks for the detailed = explanation. I have=20 read this several times and will give it further study. We agree that = mass, by=20 definition, will be independent of the setting and that weight will vary = depending upon gravity. </FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> But even the determinations = of mass on=20 an equal-beam balance will be influenced by ambient gas pressure unless = the=20 reference mass and the unknown mass have equal volume. And a beam = balance will=20 register noise (I expect) at zero gravity.</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> Going to the moon to test this is = expensive=20 and, in any case, one would need permission of the owners. It is = more=20 convenient to consult a Quantitative Chemistry text. If the = unknown=20 object is not as dense as the reference, then 'mass' of the unknown will = appear=20 to increase when gas is removed from the balance. And my Quantitative = Chem. text=20 states that "Thus the mass of the object in vacuum is greater than that = measured=20 in air..."</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> But, on the other hand, if the = unknown is=20 more dense than the reference then 'mass' of the unknown will appear to = have=20 decreased when gas is removed. Wow we have just created and destroyed = matter=20 with a vacuum pump. </FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2></FONT><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> It gets much worse if you use a = weighing=20 system in which no reference 'mass' is concurrently used, e.g. a = spring=20 scale calibrated on earth using a series of references 'masses'. The = mass will=20 appear to be much less on the moon and become zero at zero = gravity.</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> Therefore, even an equal-beam = balance does=20 not really measure mass. It is responding to F which is equal to mg, the = two=20 arms being in balance when the reference F, by nature of the equipment = design,=20 applies an upward force F that equals the downward F of the unknown when = the two=20 are in balance.</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> I suspect that the different = conventions=20 over time reflect different contexts. If you dealt with objects at rest = (e.g.=20 preparation of reagents) then weight would be standard usage = (sometimes=20 called mass to appear learned). If you dealt with objects in motion then = mass=20 would be standard. </FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> Units are only as good as they = are useful.=20 I notice that spring scales are now calibrated in Newtons. How would one = check=20 that calibration ? With a box of standard Newton Forces ?=20 </FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> It will just take a while and=20 probably a fresh set of participants to make the adjustment. = </FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> I still buy apples by the pound = but to=20 prepare for the changeover; a Newton of apples will be one apple. = Right=20 ?</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2>Yt, Dave Webster, Kentville</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2> </FONT> </DIV> <BLOCKQUOTE=20 style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; = PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"=20 dir=3Dltr> <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV> <DIV=20 style=3D"FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: = black"><B>From:</B>=20 <A title=3Dpatrick.kelly@dal.ca = href=3D"mailto:patrick.kelly@dal.ca">Patrick=20 Kelly</A> </DIV> <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A = title=3Dnaturens@chebucto.ns.ca=20 href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto.ns.ca</A> = </DIV> <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Saturday, September 22, = 2012 11:28=20 AM</DIV> <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: [NatureNS] = Correction; Fw:=20 Velocity of light</DIV> <DIV><BR></DIV>I'm not sure I see the confusion arises over the kg = being a=20 unit of mass. I just covered this in my last astronomy class and why = people=20 use the words mass and weight interchangeably when they are two = totally=20 different things. Mass is a measure of how much matter an object = contains. You=20 measure mass with a scale. A 1 kg bag of sugar has the same mass here = as well=20 as on the Moon, as on a scale you would still need a 1kg mass to = balance it. <DIV><BR></DIV> <DIV>Weight is a force, not a measure of mass. The problem is not = helped when=20 people still use the English unit of "pound" for both weight and mass. = The=20 English system unit of mass is the slug, not the pound. Your weight is = the=20 force of gravity acting on your mass and depends on your mass, the = mass of the=20 Earth and the radius of the Earth. if you are standing on the Moon = (different=20 mass and radius) you will "weigh" less because the gravitational force = is=20 less. If you stood on a doctor's scale on the Moon you would find that = your=20 mass is the same as it is on Earth.</DIV> <DIV><BR></DIV> <DIV>In the metric system, the unit of force is the Newton (the symbol = is N).=20 1 N is the force that is required to accelerate a 1 kg mass at the = rate of 1=20 m/s/s. (i.e. Force =3D mass X acceleration). </DIV> <DIV><BR></DIV> <DIV>At the surface of the Earth, the gravitational force =3D G x m x = M / (r x=20 r), where G is the gravitational constant, m is the mass of a small = object=20 (like a person), M is the mass of the Earth and r is the radius of the = Earth.</DIV> <DIV><BR></DIV> <DIV>If you drop that small object, this force will also produce an=20 acceleration (because Force =3D mass X acceleration). So F =3D m = x a. Since=20 the force comes from gravity:</DIV> <DIV><BR></DIV> <DIV>m x a =3D G x m x M / (r x r)</DIV> <DIV><BR></DIV> <DIV>Note that since the small object is on both sides of the = equation, you=20 can cancel it, and thus you get:</DIV> <DIV><BR></DIV> <DIV>a =3D G x M / (r x r)</DIV> <DIV><BR></DIV> <DIV>This acceleration gets a special symbol, g, and has a value of = 9.8 m/s/s=20 (which you can round of to 10 m/s/s). This is the rate at which = <B>all</B>=20 objects at the surface will fall (in a vacuum). If you go to the Moon, = since M=20 and r are different the surface gravity there is much lower, 1.7 m/s/s = of=20 about 1/5 that of the Earth.</DIV> <DIV><BR></DIV> <DIV>You can also use the surface gravity as a quick way to calculate = your=20 "weight" by multiplying your mass (in kg) by g. A 1 kg mass has a = "weight" of=20 9.8 N and a person such as myself with a mass of about 100 kg would = have a=20 weight of 980 N. Thus a proper metric scale would NOT be graduated in = kg, but=20 in Newtons. I expect there are two reasons they don't. One is that = most people=20 would freak if their "weight" appeared to be 10 times what they = thought it=20 was, and secondly, since they assume you are using the scale at the = Earth's=20 surface, they have "converted" the force back into "mass". Just don't = take it=20 to the Moon and expect it to work properly!</DIV> <DIV><BR></DIV> <DIV>Pat</DIV> <DIV><BR></DIV> <DIV>PS: For those who are curious, a mass of 1 slug has a weight at = the=20 Earth's surface of 32 pounds.</DIV> <DIV><BR></DIV> <DIV><BR></DIV> <DIV><BR> <DIV> <DIV><BR></DIV> <DIV>The kg a unit oef mass <BR> <DIV> <DIV>On Sep 22, 2012, at 9:58 AM, David & Alison Webster = wrote:</DIV><BR=20 class=3DApple-interchange-newline> <BLOCKQUOTE type=3D"cite"> <DIV>Hi Fred & All,=20 = &= nbsp; Sept=20 22, 2012<BR> Explanations of weight/mass usually resemble = inconsistent confessions obtained by torture but I guess that is ok=20 now.<BR><BR> It seems logical to me that weight should be = treated=20 as a special case of F=3Dma where a in this case is g and F is = measured by=20 exerting an equal and opposite force upward to keep the mass from=20 falling.<BR><BR> One could then determine the magnitude = of mass=20 as F/g and then proceed to work out units of momentum, inertia etc = from=20 there.<BR><BR> But unfortunately kg has been defined (or = perhaps=20 redefined) as a unit of mass which leads to everything being a = hopeless=20 muddle.<BR><BR> I would try to reform the system of units = dealing=20 with weight, mass and distance but I am tied up this = afternoon.<BR><BR>Yt,=20 Dave Webster, Kentville<BR>----- Original Message ----- From: "Fred=20 Schueler" <<A=20 href=3D"mailto:bckcdb@istar.ca">bckcdb@istar.ca</A>><BR>To: = <<A=20 = href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto.ns.ca</A>><B= R>Sent:=20 Friday, September 21, 2012 9:19 PM<BR>Subject: Re: [NatureNS] = Correction;=20 Fw: Velocity of light<BR><BR><BR> <BLOCKQUOTE type=3D"cite">Quoting David & Alison Webster <<A=20 = href=3D"mailto:dwebster@glinx.com">dwebster@glinx.com</A>>:<BR></BLOCK= QUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite">I just dug out my 1st yr Physics (Weber, = White=20 & Manning, 1952) and they consistently refer to 'speed = of=20 light' as opposed to 'velocity of light'. Four other = sources=20 (1941, 1948, ~1965 &1962) have = velocity.<BR></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">* indeed, it would be ineffective to purge = society, or even literature, of all who misuse = speed/velocity or=20 weight/mass. Or, to bring it closer to natural history, all = who=20 refer to nonhemipterans as "bugs."<BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">fred.<BR></BLOCKQUOTE> <BLOCKQUOTE=20 = type=3D"cite">=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D<BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite">----- Original Message ----- From: = "David &=20 Alison Webster" <<A=20 = href=3D"mailto:dwebster@glinx.com">dwebster@glinx.com</A>><BR></BLOCKQ= UOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite">To: <<A=20 = href=3D"mailto:NatureNS@chebucto.ns.ca">NatureNS@chebucto.ns.ca</A>><B= R></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite">Sent: Friday, September 21, 2012 7:44=20 PM<BR></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite">Subject: Velocity of=20 light<BR></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite">Dear All,=20 = &= nbsp; Sept=20 21, 2012<BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> The recent discussion about = transmission=20 of electricity, reading of HEAT and reading some of = Energy...=20 brings to the forefront a question that has nagged me = for=20 decades. Perhaps someone can=20 clarify.<BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE = type=3D"cite"><BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> In the typical elementary = physics text=20 we are told that velocity is a vector quantity, and to = quote one=20 text "velocity... may be defined as the rate of change = of=20 position in a given direction". But "In cases where the=20 direction of motion does not require to be considered , = the term=20 speed is employed to express the rate of=20 travelling."<BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE = type=3D"cite"><BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> Based on the above I would think = that=20 the rate of movement of light should be called speed, = i.e. speed=20 of light but I think it is always called=20 velocity.<BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite">For example, if light from the sun is=20 reflected from two 45o mirrors then a beam of light = could be=20 directed from the earth back to the sun and, the = velocity would=20 then be minus 3 x 10^10 cm/sec. Or if variously = scattered or=20 reflected then the velocity, relative to the initial sun = to=20 earth direction, would always be less than 3 X 10^10 and = after=20 several reflections might be=20 zero.<BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE = type=3D"cite"><BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> Is there some good reason why = the speed=20 of light is termed velocity of light ? Or is it called = velocity=20 because the textbook authors forget what they said in = chapter=20 one by the time they write chaper eleven ? (And they all = copy=20 from each other)<BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite">Yt, Dave Webster,=20 Kentville<BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE=20 = type=3D"cite">-----------------------------------------------------------= -<BR></BLOCKQUOTE> <BLOCKQUOTE=20 = type=3D"cite"> Frederick = W.=20 Schueler & Aleta Karstad<BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">Bishops Mills Natural History Centre - <A=20 = href=3D"http://pinicola.ca/bmnhc.htm">http://pinicola.ca/bmnhc.htm</A><BR= ></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">Mudpuppy Night in Oxford Mills - <A=20 = href=3D"http://pinicola.ca/mudpup1.htm">http://pinicola.ca/mudpup1.htm</A= ><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">Daily Paintings - <A=20 = href=3D"http://karstaddailypaintings.blogspot.com/">http://karstaddailypa= intings.blogspot.com/</A><BR></BLOCKQUOTE> <BLOCKQUOTE=20 = type=3D"cite"> South = Nation=20 Basin Art & Science Book<BR></BLOCKQUOTE> <BLOCKQUOTE = type=3D"cite"> <A=20 = href=3D"http://pinicola.ca/books/SNR_book.htm">http://pinicola.ca/books/S= NR_book.htm</A><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> RR#2 Bishops Mills, = Ontario,=20 Canada K0G 1T0<BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> presently in Cochrane -=20 49.06274N 81.02415W -<BR></BLOCKQUOTE> <BLOCKQUOTE=20 = type=3D"cite">  = ;on=20 the great Ontario Claybelt<BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"> (613)299-3107 <bckcdb at=20 istar.ca> <A=20 = href=3D"http://pinicola.ca/">http://pinicola.ca/</A><BR></BLOCKQUOTE> <BLOCKQUOTE=20 = type=3D"cite">-----------------------------------------------------------= -<BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite"><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">-----<BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">No virus found in this = message.<BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">Checked by AVG - <A=20 href=3D"http://www.avg.com">www.avg.com</A><BR></BLOCKQUOTE> <BLOCKQUOTE type=3D"cite">Version: 2012.0.2221 / Virus Database: = 2441/5278 -=20 Release Date: = 09/19/12<BR></BLOCKQUOTE><BR><BR></DIV></BLOCKQUOTE></DIV><BR> <DIV apple-content-edited=3D"true"><SPAN=20 style=3D"WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; = BORDER-COLLAPSE: separate; FONT: medium Helvetica; WHITE-SPACE: normal; = ORPHANS: 2; LETTER-SPACING: normal; COLOR: rgb(0,0,0); WORD-SPACING: = 0px; -webkit-border-horizontal-spacing: 0px; = -webkit-border-vertical-spacing: 0px; = -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: = auto; -webkit-text-stroke-width: 0px"=20 class=3DApple-style-span> <DIV=20 style=3D"WORD-WRAP: break-word; -webkit-nbsp-mode: space; = -webkit-line-break: after-white-space"><SPAN=20 style=3D"WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; = BORDER-COLLAPSE: separate; FONT: medium Helvetica; WHITE-SPACE: normal; = ORPHANS: 2; LETTER-SPACING: normal; COLOR: rgb(0,0,0); WORD-SPACING: = 0px; -webkit-border-horizontal-spacing: 0px; = -webkit-border-vertical-spacing: 0px; = -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: = auto; -webkit-text-stroke-width: 0px"=20 class=3DApple-style-span> <DIV=20 style=3D"WORD-WRAP: break-word; -webkit-nbsp-mode: space; = -webkit-line-break: after-white-space"><SPAN=20 style=3D"WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; = BORDER-COLLAPSE: separate; FONT: medium Helvetica; WHITE-SPACE: normal; = ORPHANS: 2; LETTER-SPACING: normal; COLOR: rgb(0,0,0); WORD-SPACING: = 0px; -webkit-border-horizontal-spacing: 0px; = -webkit-border-vertical-spacing: 0px; = -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: = auto; -webkit-text-stroke-width: 0px"=20 class=3DApple-style-span> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier><BR=20 = class=3DApple-interchange-newline>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier>Patrick Kelly</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier>Director of Computer Facilities</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 = face=3DCourier>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier>Faculty of Architecture and Planning</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier>Dalhousie University</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 = face=3DCourier>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier>MAIL = =20 =20 COURIER</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3 = face=3DCourier>PO=20 Box 15000 <SPAN=20 class=3DApple-converted-space> = =20 <SPAN = class=3DApple-converted-space> </SPAN></SPAN>5410=20 Spring Garden Road</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier>Halifax, Nova Scotia B3H 4R2<SPAN=20 class=3DApple-converted-space> </SPAN><SPAN=20 class=3DApple-converted-space> <SPAN=20 class=3DApple-converted-space> </SPAN></SPAN>Halifax, Nova=20 Scotia</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier>Canada<SPAN = class=3DApple-converted-space> </SPAN><SPAN=20 class=3DApple-converted-space> = =20 <SPAN=20 class=3DApple-converted-space> </SPAN></SPAN>Canada</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 = face=3DCourier>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D</FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 face=3DCourier>Phone:(902) 494-3294<SPAN = class=3DApple-converted-space> =20 <SPAN = class=3DApple-converted-space> </SPAN></SPAN>FAX:(902)=20 423-6672<SPAN class=3DApple-converted-space> </SPAN><SPAN=20 class=3DApple-converted-space> <SPAN=20 class=3DApple-converted-space> </SPAN></SPAN>E-mail:<A=20 = href=3D"mailto:patrick.kelly@dal.ca">patrick.kelly@dal.ca</A></FONT></P> <P style=3D"MARGIN: 0px"><FONT style=3D"FONT: 12px Courier" size=3D3=20 = face=3DCourier>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D</FONT></P></SPAN></DIV></SPAN></DIV></SPAN></DIV><BR></DIV><= /DIV></DIV><A></A> <P align=3Dleft color=3D"#000000" avgcert??>No virus found in this=20 message.<BR>Checked by AVG - <A=20 href=3D"http://www.avg.com">www.avg.com</A><BR>Version: 2012.0.2221 / = Virus=20 Database: 2441/5278 - Release Date: = 09/19/12</P></BLOCKQUOTE></BODY></HTML> ------=_NextPart_000_0099_01CD98FF.5F28E350--
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