Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
MHT CET202415 May 2024Morning ShiftMathematicsVector AlgebraActual

Let a =2 i + j -2 k and b = i + j . If c is a vector such that a c =| c |,| c - a |=2 2 and the angle between ( a b ) and c is 30^ , then |( a b ) c | is equal to

Options

  1. A3 2
  2. B2 3
  3. C- 3 2
  4. D- 2 3

Correct answer

A. 3 2

Step-by-step solution

aligned & a b = | array ccc i & j & k 2 & 1 & -2 1 & 1 & 0 array | & =2 i -2 j + k & | a b |= 4+4+1 =3 ...(i) & | c - a |=2 2 & ( c - a )^2=8 aligned aligned & | c |^2+| a |^2-2 c a =8 & | c |^2+9-2| c |=8 & | c |^2-2| c |^2+1=0 & (| c |-1 )^2=0 & c =1 ...(i) & Now, |( a a ~b ) c =| c |] & =| a b | | c | 30^ & =(3)(1) ( 1 2 ) & = 3 2 aligned ...[From (i) and (ii)]

Practice Vector Algebra on Quantrex Academy →

More from Vector Algebra

P is the circumcentre of A B C . If the position vectors of A, B, C and P are a , b , c , a + b + c 4 respectively, then the position vector of the orthocentre of this triangle is 2025If the position vectors of A, B, C, D are i +2 j +2 k , 2 i - j , i + j +3 k and 4 j +5 k respectively, then the quadrilateral ABCD is a 2025The set of all real values of c so that the angle between the vectors a = cx i -6 j +3 k and b =x i +2 j +2 cx k is an obtuse angle for all real x is 2025Let a =2 i + j +3 k , b =3 i +3 j + k and c = i -2 j +3 k be three vectors. If r is a vector such that r a = r b and r c =18 , then the magnitude of the orthogonal projection of 4 2025If u , v , w are non coplanar vectors and p, q are real numbers, then the equality [ array lll 3 u & p v & p w array ]- [ array lll p v & w & q u array ]- [ array lll 2 w & q v & q 2025Let i -2 j + k , i + j -2 k , 2 i - j - k and i + j + k be the position vectors of four points A , B , C and D respectively. If a point P divides AB in the ratio 2: 1 internally an 2025If a = i + j , b =2 j - k are two vectors such that r a = b a , r b = a b , then the unit vector in the direction of r is 2025If a , b , c are three unit vectors such that a ( b c )= 3 2 b + c 2 and , are the angles between a , c and a , b respectively, then + = 2025 Full Vector Algebra list All MHT CET PYQs