631. If A=B, which of the following is not correct ?
A. A.B = A^ B^
B. |A| = |B|
C. |A^| = |B^|
D. AB^ = BA^

632. I ^. (j^ x k^) is equal to______________?
A. 1
B. i^
C. j^
D. k^

633. The direction of the vector product is given by______________?
A. Head to tail rule
B. Right-hand rule
C. Left-hand rule
D. Triangular rule

634. If east, west, north, south, up and down are representing the direction of unit vectors, then east x south has the direction along_____________?
A. West
B. North
C. Down
D. Up

635. Null vector is a vector which has________________?
A. Zero magnitude
B. No specified direction
C. Both A and B are correct
D. Both A and B are not correct

636. Which one is a unit vector ?
A. ??3 i^ + ??3 j^ + ??3 k^
B. 1/??3 i^ + 1/??3 j^ +1/ ??3 k^
C. ??3 / 3 i^ + ??3 / 3 j^ + ??3 / 3 k^
D. Both B and C are correct

637. An angle between two vectors A and B can be determined by_____________?
A. Their dot product
B. Their cross product
C. Head to tail rule
D. Right-hand rule

638. The magnitude of the cross product is equal to the dot product between them. The angle between the two vectors is________________?
A. 30°
B. 45°
C. 60°
D. 180°

639.Torque is defined as______________?
A. Turning effect of force
B. Cross product of position vector and force
C. Product of force and moment arm
D. All A, B and C are correct

640. The dimension of torque is______________?
A. [ML2T-2]
B. [MLT-2]
C. [ML2T]
D. [ML-2T-2]