A learn's puzzle on transformation equation

  • Context: Undergrad 
  • Thread starter Thread starter atreess
  • Start date Start date
  • Tags Tags
    Puzzle Transformation
Click For Summary

Discussion Overview

The discussion revolves around the transformation equation in classical mechanics, specifically the inclusion of time as a variable in the equation. Participants explore the implications of having time as an independent variable alongside other coordinates and its effect on degrees of freedom in a system.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the necessity of including time in the transformation equation, suggesting that the position coordinates should be sufficient to determine the state of the system.
  • Another participant acknowledges that while the coordinates can have implicit time-dependence, it is also possible to define new coordinates that explicitly depend on time.
  • A different participant raises a concern about degrees of freedom, arguing that if time is included as a variable, it implies that one of the coordinates must be dependent, which could affect the system's degrees of freedom.
  • Another participant speculates that time may represent the change of constraints over time, seeking clarification on this point.

Areas of Agreement / Disagreement

Participants express differing views on the role of time in the transformation equation, with no consensus reached on whether time should be included as an independent variable or its implications for degrees of freedom.

Contextual Notes

The discussion highlights potential limitations in understanding the relationship between time and the independent coordinates, as well as the implications for degrees of freedom in mechanical systems. There are unresolved questions regarding the definitions and dependencies of the coordinates involved.

atreess
Messages
4
Reaction score
0
Hi, I'm a new learner of CM and I was stuck at the very beginning. TT
The transformation equation is ri=ri(q1,q2,...,qn,t)
I wonder why t should be in the bracket.
Aren't r determined by these independent coordinates? Isn't t already contained in them?
 
Last edited:
Physics news on Phys.org
atreess said:
Hi, I'm a new learner of CM and I was stuck at the very beginning. TT
The transformation equation is ri=ri(q1,q2,...,qn,t)
I wonder why t should be in the bracket.
Aren't r determined by these independent coordinates? Isn't t already contained in them?

Certainly the [itex]q_{i}[/itex] can have some time-dependence, and that gives [itex]r_{i}[/itex] implicit time-dependence. But, you can also choose to define some new coordinates [itex]r_{i}[/itex] with explicit dependence on time.

For example, consider a particle in 1-D motion described by [itex]x(t)=v_0t[/itex]. There is no reason you can't define a new variable [itex]q(x,t)=3x+a_0 t^2[/itex], if you have some use for that transformation.
 
Thanks very much for your reply!
But how about the degrees of freedom? A system with n degrees of freedom just needs n independent coordinates. If adding t, there must be one coordinate(q1, q2,..., or t) which is dependent. :confused:
 
I guess that t represents the change of the constraint with time. Is it right?
 
Last edited:

Similar threads

Replies
0
Views
1K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 29 ·
Replies
29
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K