1.

Dot products of a vector with vectors ` hat i- hat j+ hat k , 2 hat i+ hat j-3 hat k a n d hat i+ hat j+ hat k`are respectively 4, 0 and 2. Find the vector.

Answer» Let the required vector be `(x hat(i)+y hat(j)+z hat(k))`. Then,
`(x hat(i)+y hat(j)+z hat(k)). (hat(i)-hat(j)+hat(k))=4 implies x-y+z=4` ...(i)
`(x hat(i)+y hat(j)+z hat(k)). (2hat(i)+hat(j)-3hat(k))=0implies 2x+y-3z=0`. ...(ii)
`(x hat(i)+ y hat(j)+ z hat(k)).(hat(i)+hat(j)+hat(k))=2implies x+y+z=2` ...(iii)
On subtracting (i) from (iii) we get `2y=-2 implies y=-1`.
On adding (i) and (ii), we get `3x-2z=4` ...(iv)
On adding (i) and (iii), we get `2x+2z=6` ...(v)
On solving (iv) and (v), we get `x=2` and `z=1`.
`:. x=2, y=-1` and `z=1`
Hence, the required vector is `(2hat(i)-hat(j)+hat(k))`.


Discussion

No Comment Found

Related InterviewSolutions