Exam question t/f

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

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

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.

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

LCKurtz
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 $|2\vec v|$?

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!

LCKurtz
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.

vela
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.

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!

Mark44
Mentor
If v happened to be perpendicular to itself, the original statement wouldn't be true.:tongue:

(The zero vector not included, of course.)

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!

Mark44
Mentor
Math humor...

A nonzero vector can't be perpendicular to itself.

LCKurtz