Question

Question 4.27 A vector has both magnitude and direction. Does it mean that anything that has magnitude and direction is necessarily a vector? The rotation of a body can be specified by the direction of the axis of rotation, and the angle of rotation about the axis. Does that make any rotation a vector?

Chapter Motion In A Plane Page 88

Answer 1

No !! Vector means it has magnitude as well as direction but it treats with help of vector rule ( parallelogram rule ), not with help of simple algebraic rule . A best example of it is "Current" it have both magnitude as well as direction but "current doesn't consider in vector quantity. Because it can be added or subtracted with help of simple algebraic rule not parallelogram rule .

The finite rotation of a body about an axis isn't a vector even though has magnitude as well as direction because it doesn't obey vector rule for addition.
But infinitesimal rotation is a vector quantity because it obey the law of vector addition or subtraction .