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conversions

Postby guest » Fri Jan 30, 2004 11:14 am

What do all conversion factors have in common?
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Re: conversions

Postby Knight » Mon Feb 02, 2004 10:47 pm

guest wrote:What do all conversion factors have in common?

http://www.convert-me.com/en/bb/viewtopic.php?t=156
William J. Knight
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conversion factors all contain ...

Postby moe » Mon Sep 20, 2004 4:33 am

all conversion factors contain a "factor-of-one",
which when multiplied by a number with its unit
will convert one measuement to a number and a different unit

each factor-of-one has a number and at least two units

for example a question like: how many metres are in one inch

will look like this in symbol form:

2 inch = ? metres

the symbols for inches could be in, inch, inches or " ... there is no standard

since 1 in = 0.0254 m

the factor-of-one will be

0.0254 m/in

to convert 2 inches to metres in symbols:

1 in * 0.0254 m/in = 0.0254 m

notice that the inches cancel nicely and one is left with metres

there are few sites which do this math properly ... most just multiply by some number and the units just appear ... but this is poor math and also does not teach the learner how to go on and do other related question. this poor math method is employed in schools by teachers that are poorly prepared in this simple math skill
moe
 

Re: conversion factors all contain ...

Postby Knight » Mon Sep 20, 2004 9:33 pm

moe wrote:all conversion factors contain a "factor-of-one",
which when multiplied by a number with its unit
will convert one measuement to a number and a different unit

each factor-of-one has a number and at least two units

for example a question like: how many metres are in one inch

will look like this in symbol form:

2 inch = ? metres

the symbols for inches could be in, inch, inches or " ... there is no standard

since 1 in = 0.0254 m

the factor-of-one will be

0.0254 m/in

to convert 2 inches to metres in symbols:

1 in * 0.0254 m/in = 0.0254 m

notice that the inches cancel nicely and one is left with metres

there are few sites which do this math properly ... most just multiply by some number and the units just appear ... but this is poor math and also does not teach the learner how to go on and do other related question. this poor math method is employed in schools by teachers that are poorly prepared in this simple math skill

Thanks Moe!

This is a point that I try to make clear in explainations here, but you've made it an excellent lesson unto itself.

A couple of sticking points, minor though they be:

1)There actually is a standard to the US Customary measures, drawn out in the Omnibus Trade and Competitiveness Act of 1988. The standard unit for inches is "in" as in 12 in/ft.

For length the units are:

12 Inches (in)
12 in = 1 foot (ft)
3 ft = 1 Yard (yd)
16.5 ft = 1 Rod (rd)
40 rd or 220 yd = 1 furlong (fur)
8 fur = 1 mile (mi)

There is a good reference with conversions to proper SI units available at http://en.wikipedia.org/wiki/U.S._customary_units


2) To convert 2 inches to metres in symbols would not be:

1 in * 0.0254 m/in = 0.0254 m

Rather, it would be 2 in * 0.0254 m/in = 0.051 m
William J. Knight
Health Physicist
Los Alamos National Labs
User avatar
Knight
Expert
 
Posts: 309
Joined: Tue Jan 13, 2004 9:43 pm
Location: Los Alamos, NM


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