v X mv =0 ??? why
v denotes velocity and mv denotes momentum, both velocity and momentum are in the same direction, the angle between them is 0o . Note that m is scalar and v is a vector quantity, if we multiply a scalar m with a vector v, then resulting quantity mv is a vector whose direction is in the direction of v
the formula of cross product involves sine of angle between the two vectors. Here sin(0) = 0
v X mv = |v||mv| sin(0) = 0