where {displaystyle homega =2pi /T} {displaystyle homega =2pi /T} and T is the time taken for the stick to move from one groove to the next; {displaystyle Y} Y is some unknown scaling factor that characterizes the force with which the two sticks are pressed against one another. By rubbing a finger against these grooves on the side, one can also introduce a horizonal alternating driving force {displaystyle F_{x}} F_x