Unit Vectors Homework: Vector A-B & Magnitude

[chocolatelover]

Homework Statement

Vector A=3i-1j and B=-i-4j
Find vector A-B and|vector A-B|

Homework Equations

The Attempt at a Solution

Vector A-B=4i-3j

Is the |vector A-B|the magnitude or just the absolute value of the answer?

Thank you very much

 

[ranger]

|A| is the magnitude of a vector A. To avoid confusion, one can use ||A|| to denote magnitude.

 

[chocolatelover]

Thank you very much

Is the other part correct? The magnitude is the same thing as the angle of the vector, right? Is there a formula for calculating the magnitude?

Thank you

 

[ranger]

The magnitude of a vector whose components are <a1, a2> (2 dimensional vector) is:

$$\sqrt{a_1^2 + a_2^2}$$
Please do not confuse magnitude and direction. Although they are both characteristics of a vector, they are different things.

Recheck A-B, the j component has its sign messed up.

 

[chocolatelover]

Thank you very much

4i+5j does that look correct?

 

[ranger]

Recheck.
Let A = <a1, a2> and B = <b1, b2>

A-B = <a1-b1, a2-b2>

 

[chocolatelover]

If vector A=3i-1j
and B=-1i-4j

in order to find A-B, don't you just do 3i--1i=4i and -1i--4j=3j

Wouldn't it be 4i+3j?

and is the magnitude of A-B 6.40?

Thank you

 

[ranger]

Yup 4i+3j is correct. You made the mistake of writing 4i-3j in your initial post.

 

[chocolatelover]

Thank you very much

Regards

 

[ranger]

But your magnitude doesn't look too good. Recheck that.

 

[chocolatelover]

Thank you