Units Overview - mkraska/meclib GitHub Wiki

There are various ways to handle scientific units in STACK.

Variables with Units in Question Design and Input

Question Variables

Define the variables with units which are to be used for display (e.g. as given values in the question text).

stack_unit_si_declare(true); /* this initializes unit definitions */ 
F: 3*kN;
A: 4*cm^2;
sigma: F/A;

Question Text

• display of given values:

  {@'F=F@}

• place input field:

  <p>\( \sigma= \) [input:S_sigma](/mkraska/meclib/wiki/input:S_sigma) [validation:S_sigma](/mkraska/meclib/wiki/validation:S_sigma) [feedback:sigma](/mkraska/meclib/wiki/feedback:sigma)</p>

• Hide multiplication sign:

  <p>{@(make_multsgn("blank"),'F=F)@}</p>

Input

Changes of pre-sets:

Field	Value
Input type	Units (Einheiten)
Model answer	variable which stores value and unit: sigma
Input box size	8
Insert stars	Insert stars for spaces only
Syntax hint	Number with unit (Zahl mit Einheit)
Hint attribute	Placeholder
Forbid float	No
Show the validation	Yes, compact

PRT

Field	Value
Auto-simplify	No
Feedback style	Compact
Answer test	UnitsRelative
SAns	S_sigma
TAns	sigma
Test options	0.005 (requires 3 significant digits)
Quiet	Yes
False feedback	{@fb_unit(S_sigma, sigma, 0.005)@}

Unitless Question Design but Input with Units

Question Variables

Define the variables in SI unit values

F: 3*1000; /* 3 kN */
A: 4*1e-4; /* 4 cm^2 */
sigma: F/A; /* Pa */

Question Text

• display of given values:

  \( {@'F=F/1000@}\,\mathrm{kN} \)

• place input field:

  <p>\( \sigma= \) [input:S_sigma](/mkraska/meclib/wiki/input:S_sigma) [validation:S_sigma](/mkraska/meclib/wiki/validation:S_sigma) [feedback:sigma](/mkraska/meclib/wiki/feedback:sigma)</p>

Input

Changes of pre-sets:

Field	Value
Input type	Units (Einheiten)
Model answer	variable times SI-unit: sigma*Pa
Input box size	8
Insert stars	Insert stars for spaces only
Syntax hint	Number with unit (Zahl mit Einheit)
Hint attribute	Placeholder
Forbid float	No
Show the validation	Yes, compact

PRT

Field	Value
Feedback style	Compact
Answer test	UnitsRelative
SAns	S_sigma
TAns	sigma*Pa (value times SI unit)
Test options	0.005 (requires 3 significant digits)