Originally Posted by TCF
Effective mass is the mass of the racquet 'effectively' involved in a hit at a given location of the stringbed. The entire mass of the racquet is not involved during this collision, and no part of the forehand is included in effective mass.
I think you are right in this context of the TWU prof.
I was thinking of something else I had read when people do momentum calculations of the racket hitting the ball and want to know what mass to use. This case probably refers to only a part of the racket.