Spin Orientation Issues


There is a ball placed in some air current and there is air passing through it both at its upper side and lower side. The ball will rotate under the influence of air current. In this situation, what is meant by top spin and bottom spin? Why is it called top of bottom but not clockwise or anticlockwise spin? Is there any special meaning of the words top and bottom?


There is always confusion possible in designating the direction of rotation. Clockwise and anti-clockwise are really not anything special. They just reflect an arbitrary choice by ancient clock makers. Suppose you and I were on opposite ends of the axis of a rotating disk. If you see the rotation as clockwise then I will see it as anti-clockwise. Top and bottom spin, left and right spin, up and down spin are terms that you may hear used to describe the orientation of rotation. About the only agreement we can get among different observers is that for an object with a fixed axis of rotation there are two spin states. It does not matter much what we call them. The point is there is something fundamentally different about one spin orientation and its reverse.

To me, top spin means the top of a golf ball for example is moving due to its rotation in the same direction as its flight. Bottom or back spin is the reverse of this.