"Speed" "Velocity" are Different Terms 4-1-05

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=90 BGCOLOR="#006699" TEXT="#080000" background="042d05a3.jpg"> <div> <FONT SIZE="5" COLOR="#000000" FACE="Arial" ><B>Big Ring Media Team, Inc.</B></FONT><B>    </B><B> |     </B><A HREF="index.htm" TARGET="_top" TITLE="Big Ring Media Team, Inc."><B>home</B></A></div> <bR> <div> </div> </td> </tr><tr> <td valign="top" width=210 BGCOLOR="#FFCC66" TEXT="#080000" background="043d2123.jpg"> <div> Click on this link to return to <A HREF="id40.htm" TARGET="_top" TITLE="Word Watch by Subject">Word Watch by Subject</A>.</div> <div> Click on this link to go to <A HREF="id39.htm" TARGET="_top" TITLE="Word Watch by Date">Word Watch by Date</A>.</div> </td> <td valign="top" height=390 width="100%" BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <I>"Speed" "Velocity" are Different Terms 4-1-05</I></div> <div> Through maltreatment and neglect, “speed” and “velocity” are becoming synonymous. There remains, however, a risk in substituting one for the other.</div> <div> In an attempt to sound learned or authentic or sincere, some writers use “velocity” when they mean “speed.” Physicists have two different terms not so that they can sound learned or authentic or sincere, but because there's a distinction in meaning. “Speed” is distance traveled per unit of time, such as miles per hour or feet per second. The unit always has both distance and time measurements, although sometimes one or the other is implied. “Light year,” for example, doesn't have an explicit distance measurement, but the unit expresses the distance light travels in one year.</div> <div> Speed is one of two components of “velocity.” The other is direction. If we say, “The car was traveling at 90 miles per hour,” we have speed. If we say, “The car was traveling north at 90 miles per hour,” we have velocity.</div> <div> Lots of writers use “velocity” incorrectly, but it seems to us that copywriters are the most frequent offenders.</div> <div> <I>The high-velocity spin cycle of the Mayfair X19 washer cuts drying time in half.</I></div> <div> We assume that the tub of the X19 spins on its axis, and that it doesn't carom about the laundry room or race up and down the street, so the direction is a given. It's true that this is an example of velocity, but since the direction is not in question, using “velocity” just sounds silly and redundant. “High-speed spin cycle” would be a better choice.</div> <div> <I>Simply attach the WalkWasher II to your garden hose and the high velocity stream of water blasts dirt and gunk from your deck, sidewalk, driveway - even your gutters.</I></div> <div> If we were writing this, we wouldn't use “velocity” because the direction of the water is understood (the stream comes straight out of the end of the WalkWasher II) and because the final direction is controlled by the user and is not really a function of the WalkWasher II itself. Lay the hose on the ground with the water turned on to see whether the WalkWasher II is selective in its direction.</div> <div> Besides, the velocity of the stream isn't doing the work. The force of the stream is what cleans the surface. You may recall that f=ma, or force equals mass times acceleration. Direction plays no role here, other than the fact that the user must direct the force at the offending gunk. So if indeed we were writing this, we'd say something like, “Simply attach the WalkWasher II to your garden hose and the forceful stream of water...”</div> <div> In summary, use “velocity” only when direction is provided and plays a role in the description. Where direction is implied or understood, or where it has no role in the matter, use “speed.”</div> </td> </tr></table></body>