Forces between charges. Did the problem, have question on the result.

[frozenguy]

Homework Statement

Three point charges are located at the corners of an equilateral triangle with side length a=0.50m

Homework Equations

The Attempt at a Solution

My question is how can I subtract the vector F_2/1? Vectors can't be negative right? I found the magnitude of the vector to be negative. Should I have not included the negative sign for the 4 micro coulomb charge? Then I add the two vectors and that will give me the correct result.

My result is correct, but I can't minus vectors so I kind of did it illegally ya?

Thanks for your help.

 

[Hellabyte]

Why do you think that vectors can't be negative? You can subtract vectors with no problem, whoever told you this was wrong. A negative vector is an arrow pointing in the opposite direction of whatever the unit vector is. basically the vector itself isn't negative, but the magnitude is negative. for example if I have a vector 3x (3 in the x direction) it represents an arrow of magnitude 3 pointing in the x direction. --->. A vector -3x (-3 in the x direction) just represents an arrow of magnitue -3 in the x direction. <---. Don't get confused by the term "vector addition". When we subtract, all we are really doing is adding a negative number. Subtracting vectors is solely adding vectors of negative magnitude. Which is totally fine.

 

[frozenguy]

Why do you think that vectors can't be negative? You can subtract vectors with no problem, whoever told you this was wrong. A negative vector is an arrow pointing in the opposite direction of whatever the unit vector is. basically the vector itself isn't negative, but the magnitude is negative. for example if I have a vector 3x (3 in the x direction) it represents an arrow of magnitude 3 pointing in the x direction. --->. A vector -3x (-3 in the x direction) just represents an arrow of magnitue -3 in the x direction. <---. Don't get confused by the term "vector addition". When we subtract, all we are really doing is adding a negative number. Subtracting vectors is solely adding vectors of negative magnitude. Which is totally fine.

Ok, that sounds very familiar to how I studied it in math.

I don't know why I can get confused with vectors.. I think its because my intro to physics teacher said that only magnitudes (scalars) are positive. If your vector comes up negative, you have initially set it in the wrong direction.

I know part of that is true, or maybe all if it in a way, I just interpreted the first part wrong I think..

So the work I wrote is correct? By adding the vectors, I subtract the components of F_2/1 from F_3/1

 

[Hellabyte]

Yeah it looks fine to me, i don't have time to look into detail. You should talk to your physics teacher and tell him that the way he is saying it is confusing. I am sure he will appreciate feedback on his teaching.