**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]