Correct Response: A. Angular momentum is a vector quantity. The conservation of angular momentum accounts for the rotation of the chair that takes place with a vector angular momentum, which when added to the final vector angular momentum of the wheel equals the initial vector angular momentum of the wheel. Answer choice B could be used to explain the precession of the bicycle wheel if it were held by only one end of its rotational axis, but it does not help explain the rotation of the chair in this case. Answer choice C does not apply, since rotational kinetic energy is not conserved. Answer choice D does not explain the rotation of the chair, although the chair-wheel system does involve two axes of rotation.
