|
All questions about conversion can be solved by
going there:
The Rowletts Dictionay of Units,
Han
----- Original Message -----
Sent: Saturday, 2004-12-25 22:33
Subject: [USMA:31715] Re: Cubic
feet
On 2004 Dec 24 , at 8:10 PM, john mercer wrote:
I
have a question about converting cubic feet to liters. Is the conversion
factor between cu ft and liters one cu ft = 27 liters?
To all:
Am I being unreasonable in thinking that John should be able to figure
these things out himself?
==============
To John,
I have a
question about why you can't figure these things yourself.
Do you not
have access to any list of conversion factors for the basic measurements? From
those, you can easily calculate conversions for any compound units like cubic
feet. (Of course, if you have a thorough list of conversion factors, it might
have the specific conversion you need already listed and you wouldn't need to
figure it out.)
For example:
You should know (I hope) metric
relations such as:
1 L = 1000 cm^3
100 cm = 1 m
If you grew up in a
place that uses Ye Olde english units, you should also know:
1 ft. = 12
in.
These above plus ONE conversion factor relating any metric length to
any Olde English length is the only additional information needed. You may
know (or can easily look up) that 1 in. = 2.54 cm. (That's exact, by law, and
I happen to know it, but you could look it up.)
So here goes
(converting 1 cubic foot into litres):
Start by writing 1 cubic foot = 1
cubic foot. That's obvious, but bear with me; it makes it easier to keep
organized if you start that way.
1 ft^3 = 1 ft^3
To convert from
feet to inches (and cubic feet to cubic inches), multiply the right side by 12
inches per foot, since there are 12 inches in one foot, and do it three times,
since cubic feet is the same as ft x ft x ft. (The _expression_ on the left side
of the equals sign stays the same.)
1 ft^3 = (1 ft^3) x (12 in/ft) x
(12 in/ft) x (12 in/ft)
Use you calculator to get 1 x (12 x 12 x 12) =
144 so that now you have the result in cubic inches instead of cubic
feet.
1 ft^3 = 1728 in^3
Now use the fact that there are 2.54
centimetres per inch (2.54 cm / in.) to convert the inches to centimetres (and
cubic inches to cubic centimetres, by doing this three times also (since the
inches are cubed); that is multiply the right side by 2.54 cm/in. three times
(leaving the left side alone):
1 ft.^3 = 1728 in^3 x (2.54 cm/in. x
2.54 cm/in. x 2.54 cm/in.)
Use your calculator to find that 1728 x
(2.54 x 2.54 x 2.54) = 28316.8...
1 ft.^3 = 28316.8...
cm^3
Round this reasonably, consistent with what you're going to do
with the results. I'd call it:
1 ft^3 = 28300 cm^3
Now convert
this to litres using the fact that there are 1000 cm^3 per litre. This time we
have to divide the right side by the 1000 because we already have cubic
centimetres and we're looking for litres.
DON'T use your calculator to
divide by 1000 because this step is so easy to do in your head (as is usually
the case when we are in the metric system):
1 ft^3 = 28.3
L
(Notice that I never did anything at all to the left hand side of the
equals sign. But it leaves me with an _expression_ that is easy to understand
and I think it helps to write it that way.)
ALL conversions can be
carried out in the same way. You need one conversion factor from Olde English
to metric for each type of quantity involved (here, we had just one type:
length). Then convert all the old units in the old system to that particular
old unit for which you know the conversion factor. (Here we had to convert
feet to inches since we had a conversion factor for inches.) Then convert from
Olde English to metric. Finally (if necessary) convert the SI unit you get
into the SI unit you want. (Here we had to convert from cubic centimetres to
litres.)
PS
In case you are not already aware of the problem of
writing squares and cubes in email, I will note that I have used cm^3 for
centimetres, etc. because I cannot write the superscript 3 for
"cubed".
Regards,
Bill Hooper
Fernadina Beach, Florida,
USA
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Go Metric America! Or get left
behind!
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
