Clarifying the Relationship between A and B

[Noxide]

If I want to find A relative to B, what am I really looking for?

Am I assuming that A is fixed at the origin and looking at B's motion compared to A, or the converse?

Could someone please clarify this for me.

Also, does the same thing apply to with respect to?

A with respect to B?
This means that B is fixed and we're looking for A compared to B right?

Just a little clarification needed!

Thanks

 

[diazona]

What are A and B? The way you're phrasing your questions, it sounds like A and B are particles, and in that case finding A with respect to, or relative to, B, makes no sense. It's like asking how to calculate your chair relative to your keyboard.

What I'm guessing you're actually asking is how to find the velocity of A relative to (or with respect to) B. In that case, what you would be looking for is the velocity of A in a reference frame where B is fixed at the origin. In Newtonian physics, this is just the velocity of A minus the velocity of B.

If you wanted to find, say, the electrical potential of B with respect to (or relative to) A, then it would be the potential of B minus the potential of A.