Finding vector B when B + C equals a multiple of the y axis

[B-80]

If B is added to C = 2.5 i + 3.5 j, the result is a vector in the positive direction of the y axis, with a magnitude equal to that of C. What is the magnitude of B?

I have tried 0, which seems to make sense to me, but it is wrong. and I don't know if it means b+c=2.5i+3.5j or if b=? and c=2.5i+3.5j. Also how can a resultant vector = one of its components if the other vector has any value?

 

[learningphysics]

"the result is a vector in the positive direction of the y-axis with a magnitude equal to that of C"

first calculate this vector.

 

[B-80]

okay, 4.3

 

[learningphysics]

okay, 4.3

yes, that's the magnitude... what's the vector?

 

[B-80]

idk I don't have the angle? unless the first vector they gave was the resultant? is that how it sounds to you?

 

[tabchouri]

you have the magnitude of B+C which is 4.3, you know also that B+C is in the positive direction of y
so
B + C = 4.3 j
let B = a i + b j
so
B + C = (a i + b j) + (2.5 i + 3.5 j ) = 4.3 j

the rest : what are a & b that define B ?

 

[B-80]

-2.5 + .7, so 2.6, thanks

 

[B-80]

I am also having trouble with
Here are three vectors in meters: d1 = -3.0 i + 3.0 j + 2.0 k, d2 = 2.0 i + 3.0 j + 2.0 k, d3 = -2.0 i - 6.0 j + 1.0 k. What results from the following products?

(a) d1· (d2 + d3)

(b) d1· (d2 d3)

(c) d1 (d2 + d3)

 

[dynamicsolo]

I am also having trouble with
Here are three vectors in meters: d1 = -3.0 i + 3.0 j + 2.0 k, d2 = 2.0 i + 3.0 j + 2.0 k, d3 = -2.0 i - 6.0 j + 1.0 k. What results from the following products?

(a) d1· (d2 + d3)

(b) d1· (d2 d3)

(c) d1 (d2 + d3)

The first is going to involve a dot product calculation, but there is something odd about your statement of parts (b) and (c). How is part (c) different from (a)? Please check how the rest of the problem is notated -- that is very important!

 

[B-80]

cool, got that one, but have another one:

In the product = q , take q = 3,

= 2.0i + 4.0j + 6.0k and = 138i -168j + 66k.

What then is in unit-vector notation if Bx = By?

 

[dynamicsolo]

cool, got that one, but have another one:

In the product = q , take q = 3,

= 2.0i + 4.0j + 6.0k and = 138i -168j + 66k.

What then is in unit-vector notation if Bx = By?

What is being multiplied in the product? Some number of labels in this problem aren't showing up. I wonder if you've used some feature the forum software doesn't like or whether my browser doesn't read it?

 

[B-80]

In the product F = qV + B , take q = 3,
V= 2.0i + 4.0j + 6.0k and F= 138i -168j + 66k.
What then is in unit-vector notation if Bx = By?
sorry about that

 

[B-80]

hey this is due at 11:45 est, so any help is really appriciated