RussellMc wrote:

>> Agreed. Many an exam question was corrected by me during an exam by
>> checking the units and finding something amis. VERY useful sanity check.
>=20
> As long as one has the courage of one's units.

They usually make actually sense, if you think of it.

> eg
> The unit of effectiveness of a rocket fuel is (arguably) seconds.
> (thrust.seconds per mass of fuel).

Isn't thrust a force? If so: Ns/kg =3D kg m^2 s^-3 * s / kg =3D m^2 s^-2 ??

> The unit of fuel consumption of a vehicle is area (ie length^2 =3D
> m^2)(more usually expressed here as l/100km)

That's the (vertical) area of the fuel strip that the vehicle consumes
while driving, so to speak. 10l/100km =3D 10e-3/100e3 m^2 =3D 0.1e-6 m^2 =
=3D
0.1 mm^2

Gerhard
--=20
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