Vectors 4-18-05

Vectors 4-18-05

Excellent job except for one small oversight. See my note.

Sir,

The question states, Find a vector whose Magnitude is 4.9 and whose component in the x direction is .686 times its component in the y direction,

Answer..

x=(.686 *y) Therefore, Magnitude of vector (v) = Sqrt (x^2+y^2) =4.9

So, Sqrt((.686y)^2 + y^2) = 4.9

(.686y)^2 + y^2)=(4.9)^2

y^2(1+.686) =(4.9)^2

The .686 was part of a term that was squared.

(.686y)^2 + y^2)=(4.9)^2 gives you

.686^2 y^2 + y^2 = 4.9^2 wo you would have y^2(1+.686^2) =(4.9)^2.

This would change your solution for y somewhat; the resulting answer should then give you results that check out.

y^2 =((4.9)^2)/(1+.686)

y^2= 14.241 therefore y= 3.774

If x=.686 *y then x= .686*3.774 Therefore x= 2.589

I would have said v= 2.589i + 3.774j was my vector, but the sqrt(x^2+y^2) does not equal 4.9 rather 4.57

So I've done something wrong..

Can you clarify...

You caught the error. However you didn't copy down the new y component correctly when you checked your result:

y^2= 16.32 therefore y= 4.04

If x=.686 *y then x= .686*4.04 Therefore x= 2.771

I would have said v= 2.771i + 3.774j

Shouldn't this be v = 2.771 i + 4.04 j? Looks like this will just about exactly fix the discrepancy.

was my vector, but the sqrt(x^2+y^2) does not equal 4.9 rather 4.68