What is the magnitude and direction of vector C?

[rasikan]

I need help with the following questions-

1. if a= 12i+16j and b=-24+10j, what is the magnitude of the vector C=2a-b?


2.If the magnitude and direction of c are 2.5 cm and 80degree , and d[3.5cm,120degree] and e=d-2c then what is the direction of e, (to the nearest degree)?

 

[arildno]

1. What information can you use in order to find the magnitude of a vector?

 

[rasikan]

you can use any formulas..

 

[arildno]

So which one would YOU pick?

 

[rasikan]

I would use square root of (Ax)^2+ (Ay)^2

 

[arildno]

Indeed, smart choice!

So, what info are you at present lacking in order to calculate the magnitude?

And:
How can you OBTAIN that necessary information?

 

[rasikan]

no i got my answer as 64, just want to verify that, and I dnt have no clue about the second question

 

[arildno]

Well, I don't bother to calculate myself all the way to 64 or to any other dumb number, I want to find out:
HOW did you are at whatever number you got?

 

[rasikan]

can u help me with my second question

 

[arildno]

The degrees are measured with respect to the positive x-axis.
So:
How can that help you?

 

[rasikan]

well i really don't know

 

[arildno]

Well, how har the horizontal&vertical components of a vector related to the vector's magnitude and the angle the vector makes with the positive x-axis?

 

[rasikan]

i think it get calcuate arc tan of Ax/Ay

 

[arildno]

No!
Go back to your book, and read your definitions again.

 

[robphy]

i think it get calcuate arc tan of Ax/Ay

Check it for some special cases...
What angle do you expect? and What do you get with your formula?
- for a vector along the x-axis.
- for a vector along the y-axis.

 

[berkeman]

Moved from Advanced Physics to Intro Physics.