Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Options
Go to last post Go to first unread
Offline Razonar  
#1 Posted : 17 June 2020 19:30:25(UTC)
Razonar


Rank: Advanced Member

Groups: Registered
Joined: 28/08/2014(UTC)
Posts: 561
Uruguay

Was thanked: 312 time(s) in 197 post(s)
Hi. This is a small utility for see the dimensions of a unit.

dimensions.sm (62kb) downloaded 36 time(s).
dimensions.pdf (98kb) downloaded 53 time(s).

Best regards.
Alvaro.
thanks 1 user thanked Razonar for this useful post.
on 18/06/2020(UTC)
Offline Jean Giraud  
#2 Posted : 17 June 2020 20:02:36(UTC)
Jean Giraud


Rank: Advanced Member

Groups: Registered
Joined: 04/07/2015(UTC)
Posts: 4,899
Canada

Was thanked: 802 time(s) in 636 post(s)
Notice that can't find torque.
Torque is just visual popular equivalent of force ... kgf, kN
Offline Razonar  
#3 Posted : 18 June 2020 02:28:53(UTC)
Razonar


Rank: Advanced Member

Groups: Registered
Joined: 28/08/2014(UTC)
Posts: 561
Uruguay

Was thanked: 312 time(s) in 197 post(s)
Originally Posted by: Jean Giraud Go to Quoted Post
Notice that can't find torque.
Torque is just visual popular equivalent of force ... kgf, kN


Hi. Things don't turns by forces, but by torques. You can't open nor close a door just applying a force, you must to apply a torque equal to some force by it's distance to the axis of rotation, which have dimensions of energy.

Best regards.
Alvaro.
Offline mkraska  
#4 Posted : 18 June 2020 10:04:34(UTC)
mkraska


Rank: Advanced Member

Groups: Registered
Joined: 15/04/2012(UTC)
Posts: 1,638
Germany

Was thanked: 912 time(s) in 574 post(s)
Originally Posted by: Razonar Go to Quoted Post
Originally Posted by: Jean Giraud Go to Quoted Post
Notice that can't find torque.
Torque is just visual popular equivalent of force ... kgf, kN


Hi. Things don't turns by forces, but by torques. You can't open nor close a door just applying a force, you must to apply a torque equal to some force by it's distance to the axis of rotation, which have dimensions of energy.

Best regards.
Alvaro.


Judging the physical dimension from base units is not really more than just guessing. Energy and torque are just examples of that. Stress and energy density or frequency and angular velocity are other ones. Such issues frequently pop up in the forum.

Not even speaking of quantities defined by unitless ratios like strain and angle. What about material properties? Even such innocent units like Newtons could be J/m, e.g. line energy in welding.

In a sense you try to guess physical meaning from the mathematical representation. Units in SMath support this process to a really useful extend, but aren't unique.
SMath can't know what the appropriate unit for a result would be. But the user can specify expected units and whether the units match.

A clean solution isn't possible without some sort of quantity tag for variables and constants. The user needs to assign the tag upon definition, either implicitly by assigning a unit, or in case of ambiguity, gets a hint on what the assumption is and how to change that (perhaps in the help text for the unit).
We partially have such tagging with the Delta tag for temperature units to indicate differences of temperatures. But that is a tool-specific solution which isn't obvious for new users It is enforced by the added complexity, that we have different conversion rules based on what the physical meaning is.

A good system for physical dimensions is one that doesn't allow you to add quantities (variable or constant) of different dimensions even if the units match.


Martin Kraska

Pre-configured portable distribution of SMath Studio: https://en.smath.info/wi...th%20with%20Plugins.ashx
thanks 1 user thanked mkraska for this useful post.
on 18/06/2020(UTC)
Offline Jean Giraud  
#5 Posted : 18 June 2020 14:20:55(UTC)
Jean Giraud


Rank: Advanced Member

Groups: Registered
Joined: 04/07/2015(UTC)
Posts: 4,899
Canada

Was thanked: 802 time(s) in 636 post(s)
Units are just numbers between themselves ...
like saying that π = ln(2) under certain applications.
Under other applications, π = SQRT(2)
Torque = kgf*m native SI = 9.80665 N*m = 1J
.........
so many kgf applied on the wheels * so many km
= so many J = so many liters of diesel fuel = so many $.

Unit Torque.sm (34kb) downloaded 26 time(s).
Users browsing this topic
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.