(sorry about the misspelling of principal as principle oops!) This demonstration shows a fascinating observation about the rotation of a tennis racket (or pingpong paddle) is that the racket flips over if rotated freely about one of its primary axes. This is a result of Euler's Equations of Motion and the moments of inertia about the various axes being timeindependent. The socalled "Tennis Racket Theorem" applies to the case where the moments of inertia about the principal axes are spaced: I1 ≪ I2 ≪ I3. The theorem states that rotations about axes I1 and I3 are much more stable than about axis I2, even though I2 may be very close to I3 in value.