641. The unit vector in the direction of vector A = 2 i^ -2j^ + k^ is_______________?
A. 2i^ – 2j^ + k^
B. (2i^ – 2j^ +k^)/9
C. (2i^ – 2j^ +k^)/3
D. (2i^ – 2j^ +k^)/5

642. The cross product of two vectors is a negative vector when______________?
A. They are parallel vectors
B. They are anti parallel vectors
C. They are a perpendicular vector
D. They are rotated through 270°

643. In which quadrant, the only value of tan will be positive ?
A. First
B. Second
C. Third
D. Both 1st and 3rd

644. The magnitude of i^. (j^ x k^) is________________?
A. 0
B. 1
C. -1
D. i^

645. If A=Ax i^ + Ay j^ + Az K^ B = Bx i^ + By j^ + Bz K^ then______________?
A. A. B = Ax Bx + Ay By + Az Bz
B. A. B = Ax By + Ay Bz + Az By
C. A. B = Ay Bz + Az By + Az Bx
D. A. B = Ax Bz + Ay By + Az Bx

646. A central force is that which__________________?
A. Can produce torque
B. Cannot produce torque
C. Some time can produce torque some time cannot
D. Has no relation with torque

647. What is the angle that the given vector makes with y-axis and A=2i+3j ?
A. 30°
B. 60°
C. 90°
D. 120°

648. In which quadrant the two rectangular components of a vector have same sign ?
A. 1st
B. 2nd
C. Both 1st and 3rd
D. 4th

649. Two vectors A and B are making angle θ with each other. The scalar projection of vector B on vector A is written as____________?
A. A.B/A
B. A.B/B
C. A.cosθ
D. Both a and b are correct

650. Two vectors are A = 3i^+2j^ -k^& B = 3i^-2j^ +k^ , then_____________?
A. B is anti-parallel to A
B. B is a negative vector of A
C. B has a negative magnitude
D. B is perpendicular to A