JEE Main | 2018VectorHard

Question

Let u→ be a vector coplanar with the vectors a→=2i^+3j^-k^ and b→=j^+k^. If u→ is perpendicular to a→and u→.b→= 24, then |u→|2 is equal to- 

Options

A.

315

B.

256

C.

84

D.

336

Solution

u→=λ(a→×b→)×a→
=λ{a→2.b→-(a→.b→)a→}
=λ{–4i^+8j^+16k^}
u→=λ' {-i^+2j^+4k^}
u→.b→=24
⇒ λ' =4
u→=-4i^+8j^+16k^
u→=336

Create a free account to view solution

View Solution Free
Topic: Vector·Practice all Vector questions

More Vector Questions

If are three non-zero vectors, no two of them are parallel if is collinear to is collinear to then is equal to :...Angle between the vectors 2î + 6ĵ + 3 and 12 − 4ĵ + 3 is -...The p.v. of four points A,B,C,D are respectively 2î + ĵ, î − 3ĵ, 3î + 2ĵ and î ...Given the vertices A (2, 3, 1), B (4, 1, -2), C (6, 3, 7) & D (-5, -4, 8) of a tetrahedron. The length of the altitude d...The position vector of a point C with respect to B is î + ĵ and that of B with respect to A is î − ...