Ross has been reminding us recently about the need for us to use units in calculations. He has a good point, but I for one have not sought to remember the necessary conversions between various different units, like J = kg.m/s^2, as I've always calculated in straight SI units and put the units on at the end. In a discussion about it, another student pointed out this is in fact an incomplete approach, as it turns out there are only 7 fundamental units. They are:
metre for length
kilogram for mass
second for time
ampere for electric current
kelvin for temperature
candela for luminous intensity
mole for the amount of substance.
I thought this was quite interesting, not just the fact that a joule is in fact technically not an SI unit, but more for the choice of ampere for electric current. This means technically a charge can be measured properly as A.s and not C. I would argue that C is much more fundamental, as if you change reference frames a current may disappear, but a collection of charge will not. Anyone know why ampere's are chosen, or disagree with my choice of C?
On a side note, and this is for Ross and Paul. If we are expected to keep track of units, can we be given the specific units of any constants (i.e. hbar) in the final exam. Even better can we be given any units in the question in terms of the above SI units so we don't have to worry about remembering such things and can concentrate on the application of it?
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