Re: [tinspire] The TI-nSpire and prefixes.

[Sean Bird]

On your TI-Nspire CAS I would recommend pressing Catalog (the book), then 3 for units. The list and explanation is all on the handheld. For example, if you want to know what _Cc stands for (see below), then look in the catalog > units to see that it is Coulomb's Constant or 8.99*10^9 _m/_F (or N*m^2/C^2).

You are correct that all the prefixes are not available.

The following is from one of the intro pages of Nelson's conversion program for the TI-Nspire. These are the units and constants on the CAS

--- Constants: c, Cc, g, Gc, h, k, μ0, μb, Me, Mn, Mp, Na, q, Rb, Rc, Rdb, Vm, ε0, σ, φ0.
--- Length: ang, au, cm, fath, fm, ft, in, km, ltyr, m, μ, mi, mil, mm, Nmi, pc, rod, yd, Å.
--- Area: acre, ha.
--- Volume: cup, floz, flozUK, gal, galUK, l, ml, pt, qt, tbsp, tsp.
--- Time: day, hr, μs, minute, ms, ns, s, week, yr.
--- Velocity: knot, kph, mph.
--- Temperature: K, C, F, R.
--- Luminous intensity: cd.
--- Amount of substance: mol.
--- Mass: amu, gm, kg, lb, mg, mton, oz, slug, ton, tonne, tonUK.
--- Force: dyne, kgf, lbf, N, tonf.
--- Energy: Btu, cal, erg, eV, ftlb, J, kcal, kWh, latm.
--- Power: W, kW, hp.
--- Pressure: atm, bar, inH2O, inHg, mmH2O, mmHg, Pa, psi, torr.
--- Viscosity, kinematic: St
--- Viscosity, dynamic: P
--- Frequency: GHz, Hz, kHz, MHz.
--- Current: A, mA, μA, kA.
--- Charge: coul.
--- Potential: V, volt, mV, kV
--- Resistance: kΩ, MΩ, ohm, Ω.
--- Conductance: mho, mmho, siemens, μmho.
--- Capacitance: F,nF,pF,μF
--- Mag. field strength: Oe.
--- Mag. flux: Wb.
--- Mag. flux density: Gs, T.
--- Inductance: henry, mH, nH, μH.

On Mon, May 11, 2009 at 2:00 PM, Igor Pastuhovic <igor.pa...@gmail.com> wrote:

Hi!

I have a question that has been bothering me for some time now. When
using the built-in constants (for example the speed of light) the
units are added into the calculation (in this case m/s, doh). This
comes in handy since you don't have to do the conversions to SI-units
yourself in order to get the answer in SI-units; for example it does
not matter if you input 50_v*5_a or 50000_mv*5_a since the output is
the same: 250_W. However this only seems to work for certain prefixes,
typing 5_kg*_g and 5000_g*_g does not return the same value since _g
stands for the acceleration of gravity and not grams.

So my question is, is the software only designed to work with certain
prefixes or am I using it all wrong, and if that is the case is there
a list where the prefixes that can be used are showed?
Thanks!
Igor

[Nelson Sousa]

To use grams you must use the prefix _gm.

If you use the correct names for variables you'll always get proper
results. But asking 50 _kg*_g will give you a result in _N, as mass
times acceleration equals force. But, in general, you can multiply any
unit by any other and the result will be properly converted and
displayed, even if it doesn't make any sense in the real world (try
typing _Pa * _N * _c / ( _Na * _Rc ) and you'll get a nice result!).
You can only add consisten units, of course.

And also sometimes the default displayed units may not be what you're
expecting. For example, electric field can be though of as N/coul but
also V*m. The Nspire CAS displayed V*m.

Use the list Sean just posted to check the unit's names and beware of
the exceptions, namely _ton, meaning US ton (2000 _lb, I think) and
_mton, the metric ton (1000 kg); _g meaning gravitational acceleration
on Earth and _gm the metric gram; _day, _week but _min for minute, _hr
for hour and _yr for year, etc.

Once you get a grip on constant and unit names you'll get along just fine.

One single remark about the unit list: on the program I wrote for the
numeric Nspire I use minute, instead of min, as min is the name of a
function of the OS, so can't be used as a variable name. The Nspire
CAS uses _min, not _minute.


Hope this helps.

Nelson


On Mon, May 11, 2009 at 19:00, Igor Pastuhovic