The diameter in this formula is expressed as a function of x (the distance between the loading force P and the shear location) because the aim is to have a minimum tennis racket weight. Therefore, the dimensioning of the tennis racket handle is made assuming it is a uniform-strength beam. Interesting in this formula is the way the force P is expressed, as according to the adopted theory of impact in 7.2.1 the role of the forces is being played by the impact impulses. To avoid this difficulty we suggest we measure the maximum tennis racket head tip deflection from the side opposite to the collision. Then, using the formula given in 7.2.1 the force P can be expressed:
P. (Eq. 21)
3EJ
Finally, after substituting P at the respective position in the above Eq. we obtain: