# Vector

How to solve Q3.

#### Attachments

• 143.4 KB Views: 8

#### HallsofIvy

Do you know what the word "resultant" means?

#### Indranil

Do you know what the word "resultant" means?
Yes, resultant is the combined effect of two vectors. Am I correct?

#### HallsofIvy

Yes, so the "C" they refer to is the length |A+ B|. What is the relation between |A+ B| and |A- B|?

1 person

#### Indranil

Yes, so the "C" they refer to is the length |A+ B|. What is the relation between |A+ B| and |A- B|?
I don't understand the relation But as I know C = A + B (positive direction)
C = A - B A is in the positive direction and B is in the negitive direction

#### Indranil

Yes, so the "C" they refer to is the length |A+ B|. What is the relation between |A+ B| and |A- B|?
A+B is greater than A-B?

#### HallsofIvy

No, that is not necessarily true. First, do you understand the difference between "A+ B" and "|A+ B|"? Do you understand that for vectors, like A+ B and A- B, "less than" and "greater than" are NOT defined?

#### Indranil

No, that is not necessarily true. First, do you understand the difference between "A+ B" and "|A+ B|"? Do you understand that for vectors, like A+ B and A- B, "less than" and "greater than" are NOT defined?
A+B is the addition of two vectors and [A+B] is the magnitude of two vectors (addition of numbers) Am I right?

#### HallsofIvy

Yes, that is correct. And while you cannot say, of two vectors A and B, that "A< B" or "B< A", you can say that |A|< |B| or |B|< |A|.

But given two vectors (or even numbers) you cannot say "|A+ B|> |A- B|. For example, if B= -A then |A+ B|= 0 while |A- B|= 2|A|.(Nod)

1 person

#### topsquark

Forum Staff
Yes, that is correct. And while you cannot say, of two vectors A and B, that "A< B" or "B< A", you can say that |A|< |B| or |B|< |A|.

But given two vectors (or even numbers) you cannot say "|A+ B|> |A- B|. For example, if B= -A then |A+ B|= 0 while |A- B|= 2|A|.(Nod)
Good catch. I hadn't thought of that.

-Dan