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The application interface consists of three custom (A, B, C) value-units expressions and six presets, which may be added to the final expression field by pressing the corresponding buttons.
Value-Units Expression is consisting of three fields: value field, numerator (top) units field and denominator (bottom) units filed.
Units must be typed exactly as they appear in the provided list in the Help section. Power of unit is typed directly after unit : s2. Metric prefixes or unit prefixes are recognized automatically: mm = 1.0e-3 m, kA = 1000 A. Metric prefix micro- (1e-6), is changed to u! Additional Units can be added upon request through www.volard.wordpress.com.
Example of unit expression as it should appear in numerator or denominator fields: mm2*s*kg*uA-2*MPa-2.
Pressing space key while editing units or formula fields, automatically appends multiplication mark, *, to simplify the edition.
Upon addition or subtraction, unit expressions should be of the same dimensionality! Meters cannot be added to Pascals!!!
Application provides set of widely used physico-chemical constants. Pressing the corresponding constant button adds value to the final field.
Presets are: Na - Avogadro's constant, h - Planck constant, F - Faraday constant, R - gas constant, kB - Boltzmann constant, g - acceleration of gravity, e - elementary charge, Pi - pi constant. (All in SI units)
The final expression is a regular scientific formula consisting of value-units expressions, regular math operations, numbers and functions. Available math functions are provided by buttons-shortcuts. Dot is used as a decimal point.
Pressing "Calculate" button evaluates final expression. By default, application converts all units to International System of Units (SI), if not stated differently for conversion procedure.
A calculated final expression (if available) can be copied to A expression, by long pressing a "A^" button, for further conversion or calculations.
For a simple conversion, type the to be converted expression to A expression and preferred units to the B expression. Special attention should be paid to dimensionality! For example: To change m3 to US Gallon in expression s*kg/m3, type gal-1 to numerator field or gal to denominator field in the B expression. Press arrow to get the final converted result. During conversion value of B expression has no meaning.
Problem #1: What is the wavelength of an electron (mass = 9.11e-28 g) travelling at 5.31e3 km/s?
Solution: Λ = h/(m*V) , where:
Λ the wavelength of the particle
h - Planck's constant = 6.626 e-34 J*s
m – mass of particle
V – speed of particle
Planck's constant is provided by preset button (h), custom A will be the mass of particle, B – the speed of particle. The final expression: h/(A*B). Pressing (=) gives: Λ = 1.37e-10 m
Problem #2: What is a distance that a free-falling object has fallen in 50ms from a position of rest?
Solution: d = 0.5 * g * t^2
Acceleration of gravity is provided by preset button (g), custom A will be the time, then the final expression is: 0.5 * g * A^2. Pressing (=) gives: d = 0.01226 m
Problem #3: The vapour pressure of 1-propanol is 10.0 torr at 287.85K. Calculate the vapour pressure at 325.95K. Heat of vaporization of 1-propanol = 47.2 kJ/mole
Solution: Using Clausius-Clapeyron equation: PT1 = PT2*exp( (ΔHvap/R)(1/T2 - 1/T1))
1. Universal Gas constant is provided by preset button (R), custom A will be ΔHvap, custom B is T1 nad C is T2. Intermediate expression: exp( (A/R)*(1/C - 1/B)), gives 0.09972.
Apparently, 10.0 torr / 0.09972 = 100.2 torr.
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- Release Date:
- Roman Volinsky
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