Simple question about choosing coordinates

  • Context: High School 
  • Thread starter Thread starter krn93
  • Start date Start date
  • Tags Tags
    Coordinates
Click For Summary

Discussion Overview

The discussion revolves around the choice of coordinate systems in physics, particularly in relation to defining positive and negative distances and the implications for equations of motion. Participants explore how the orientation of the coordinate system affects the interpretation of distances and accelerations in a scenario involving a cliff.

Discussion Character

  • Conceptual clarification
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about whether distances below a reference point would be positive or negative based on their chosen coordinate system.
  • Another participant clarifies that a coordinate system indicates positions rather than distances, suggesting that the direction of movement relative to the defined origin is crucial.
  • A question is posed regarding the application of the equation d = volt + 1/2at², specifically whether the height of the cliff would be considered positive if gravity is defined as positive in the coordinate system.
  • A response indicates that if the origin is set at the cliff and the coordinate system increases downwards, then both gravity and the distance 'd' would be positive, but clarifies that 'd' refers to the distance an object falls, not the height of the cliff itself.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of distances and the definitions of positive and negative in the context of their coordinate systems. Multiple viewpoints are presented, leading to some confusion and clarification attempts.

Contextual Notes

There are unresolved assumptions regarding the definitions of distance and height in relation to the coordinate system, as well as the implications of initial conditions in the equations of motion.

krn93
Messages
2
Reaction score
0
Hi, i was just confused on whether certain things will be positive or negative depending on my coordinate system. Let's say I am standing on a cliff, and i make down my positive and up my negative. Would any distance below me be positive, and any distance above me be negative? Also the reference point to determine if a height is negative or positive is from where you set the origin right? Thank you.
 
Physics news on Phys.org
Any distance below you be positive? Well, not quite...any position will be positive.

A coordinate system indicates positions, not distances. If you are at the cliff, as you say, to which you had climbed without your back pack and now you define the zero of your coordinate axis right where you are and now you start pulling your back pack with a rope...your back pack will be traveling a negative distance as it reaches you even though it has been moving along the positive portion of your coordinates axis.
 
what if i was using the d=volt+1/2at^2 equation for something, and the d was the height of the cliff which I am on top off. gravity would be positive, and would my d be positive also?
 
If the zero of your coordinate system starts right at the cliff and increases down, then, yes, as gravity pulls down, 'a' would be positive and your 'd' would be positive; but 'd' is not the height of the cliff...it is the distance at which an object dropped from the cliff with initial velocity Vo would be at time 't'
 

Similar threads

  • · Replies 26 ·
Replies
26
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 12 ·
Replies
12
Views
4K
  • · Replies 8 ·
Replies
8
Views
1K
  • · Replies 22 ·
Replies
22
Views
2K
  • · Replies 3 ·
Replies
3
Views
16K
  • · Replies 29 ·
Replies
29
Views
3K