# Magnitude of the vector

1. Jan 27, 2007

### 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)?

2. Jan 27, 2007

### arildno

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

3. Jan 27, 2007

### rasikan

you can use any formulas..

4. Jan 27, 2007

### arildno

So which one would YOU pick?

5. Jan 27, 2007

### rasikan

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

6. Jan 27, 2007

### 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?

7. Jan 27, 2007

### rasikan

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

8. Jan 27, 2007

### 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?

9. Jan 27, 2007

### rasikan

can u help me with my second question

10. Jan 27, 2007

### arildno

The degrees are measured with respect to the positive x-axis.
So:

11. Jan 27, 2007

### rasikan

well i really dont know

12. Jan 27, 2007

### 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?

13. Jan 27, 2007

### rasikan

i think it get calcuate arc tan of Ax/Ay

14. Jan 27, 2007

### arildno

No!

15. Jan 27, 2007

### robphy

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.

16. Feb 1, 2007

### Staff: Mentor

Moved from Advanced Physics to Intro Physics.