Simple question about choosing coordinates

[krn93]

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.

 

[gsal]

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.

 

[krn93]

what if i was using the d=vot+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?

 

[gsal]

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'

 

[pmacias]

Hi there,

You are correct in your understanding that the choice of coordinate system can affect whether certain distances or heights are considered positive or negative. In the example you provided, if you choose to make down your positive direction and up your negative direction, then any distance below you (towards the ground) would be considered positive, while any distance above you (towards the sky) would be considered negative.

Additionally, the reference point, or origin, is where you choose to start measuring from. This can also affect whether a distance or height is considered positive or negative. For example, if you set the origin at the base of the cliff, then any distance above the base of the cliff would be considered positive, while any distance below the base of the cliff would be considered negative.

It's important to carefully consider your choice of coordinate system and origin when making measurements and interpreting data. I hope this helps clarify things for you. Let me know if you have any further questions.