# Exam question t/f

Mdhiggenz

## Homework Statement

So I took my calc 3 exam today and had this question

true or false

magnitude ( v+v) = 2*magnitude( v)

I put true.

Thoughts?

## The Attempt at a Solution

Homework Helper
Gold Member
You got it correct. Were you just guessing?

Mdhiggenz
No I did a problem where I had to solve for K in the magnitude give the value of v. Pretty much I took k from the magnitude and solved for it. So I was hoping the same thing applied here.

skiller
You got it correct.
Really? I don't see how this is correct.

Homework Helper
Gold Member
Really? I don't see how this is correct.

If ##\vec v = \langle a,b,c\rangle## what do you get for ##|\vec v|## and ##|2\vec v|##?

skiller
If ##\vec v = \langle a,b,c\rangle## what do you get for ##|\vec v|## and ##|2\vec v|##?
Sorry, of course it's correct.

I was having a senile moment when I was imagining the two vectors weren't the same! D'oh!

Homework Helper
Gold Member
Sorry, of course it's correct.

I was having a senile moment when I was imagining the two vectors weren't the same! D'oh!

Don't feel to bad about that. My first reaction was the same because I was expecting the question to read u+v since, in my opinion, that would have been a better question. Only after I started my reply did I realize the OP had v+v.

Staff Emeritus
Homework Helper
Sorry, of course it's correct.

I was having a senile moment when I was imagining the two vectors weren't the same! D'oh!
Did the same thing here.

skiller
Don't feel to bad about that. My first reaction was the same because I was expecting the question to read u+v since, in my opinion, that would have been a better question. Only after I started my reply did I realize the OP had v+v.
Did the same thing here.

I obviously need to learn to read twice before posting. Something which you two are obviously better at than me!

Mentor
If v happened to be perpendicular to itself, the original statement wouldn't be true.:tongue:

(The zero vector not included, of course.)

skiller
If v happened to be perpendicular to itself, the original statement wouldn't be true.:tongue:

(The zero vector not included, of course.)

Now you've lost me!

Mentor
Math humor...

A nonzero vector can't be perpendicular to itself.

Homework Helper
Gold Member
Math humor...

A nonzero vector can't be perpendicular to itself.

What if it's bent?