From: Matthias Troyer (troyer_at_[hidden])
Date: 2006-08-20 15:50:01
On Aug 20, 2006, at 3:09 PM, Phil Richards wrote:
> On 2006-08-20, Matthias Troyer <troyer_at_[hidden]> wrote:
>> On Aug 19, 2006, at 2:04 PM, Andy Little wrote:
>>> I was taught at school to do dimensional analysis checks manually.
>>> For example
>>> force = mass * acceleration;
>>> M = mass
>>> L = length
>>> T = time;
>>> force == M * L / T^2
>>> acceleration = L/T^2
>>> Therefore (M* L/T^2) = (M) * ( L/ T^2)
>>> In this case its just dimensional math, no value is involved.
>> This is just a check of units. I would prefer calling them units and
>> not quantities
>
> Nope, it's a check of dimensionality, not units.
>
> A check of units would be one that found an error in:
> m/s = ft/min
>
> The difference between units and dimensionality incorrectness
> is that units can be converted (if they are compatible). They
> are (sometimes) compatible when their dimensionality is the same.
>
> If your dimensionality is incorrect, you are screwed.
>
> phil, back to my rock to hide under
OK, then it checks dimensions, but still not quantities