# Homework Help: Questions on Vectors

1. Sep 4, 2007

### eraemia

1. The problem statement, all variables and given/known data

I have two questions on vectors:
1) Does the magnitude of a vector vary depending on how one chooses a reference frame?
2) Can a component of a vector be negative?

2. Relevant equations

n/a

3. The attempt at a solution

1) No, because regardless of the reference frame, the magnitude is always the same?
2) Yes, say if the vector points -y or -x or -z

2. Sep 4, 2007

### rootX

1) is wrong, I think.

because what if frame of reference is also moving at the velocity of v, where v is the velocity of the object being observed?..

3. Sep 4, 2007

### eraemia

Yeah, that makes sense. But doesn't the vector remain the same? For example, if I have a vector of 5m/s north, it remains that vector whether or not the reference frame is stationery earth or a train moving at 10m/s north... Or is the question asking like the magnitude of the object and not the vector? Sorry, I'm confusing.

4. Sep 4, 2007

### rootX

I am not sure if they are asking for resultant vector, or that original vector... (refer to those relatve motion questions)
mag. of the resultant != mag of org

yea, otherwise org. vectors remains that same vector unless some force is applied to it..

Last edited: Sep 4, 2007