0
2.5kviews
Find the transformation Av which aligns a given vector V=ai+bj+ck with the vector k along the positive z axis.
1 Answer
2
135views

enter image description here

The given vector is V = ai + bj + ck

a=0, b=1, c=1

also |¯V|=a2+b2+c2

Step 1: Rotation of vector V about X-axis by an angle θ=+θ1 {+ve indicates CCW}

Now, ,V1=bj+ck

Also,

1(V1)=b2+c2

enter image description here

From figure, sinθ1=b/b2+c2

cosθ1=c/b2+c2

Let, b2+c2=λ

So, sinθ1=b/λ and cosθ1=c/λ

Now, the rotational matrix about x-axis is,

[Rx]=[10000cosθsinθ00sinθcosθ00001]

On substituting the values of sinθ1 and cosθ1, we get,

[Rx]=[10000cλbλ00bλcλ00001]

Step 2: Rotate vector V1 about Y -axis by an angle of θ=θ2 So as to consider with z-axis.

enter image description here

From fig, sinθ2=a/a2+b2+c2=a/|V|

cosθ2=b2+c2/a2+b2+c2=λ/|V|

Now, rotational matrix about y-axis is,

[Ry]=[cosθ0sin(θ)00100sin(θ)0cos(θ)00001]

[Ry]=[λ|¯V|0(a|¯V|)00100a|¯V|0λ|¯V|00001]

[Ry]=[λ|¯V|0a|¯V|00100a|¯V|0λ|¯V|00001]

Now, combined transformation,

[Av] = [Rx][Ry]

[Rx]=[10000cλbλ00bλcλ00001][λ|¯V|0a|¯V|00100a|¯V|0λ|¯V|00001]

[Av]=[λ|¯V|0a|¯V|0abλ|¯V|cλb|¯V|0acλ|¯V|bλc|¯V|00001]

This is the matrix [Av] which aligns a given vector v=ai+bj+ck with the vector k along positive z-axis

Please log in to add an answer.