When the motion ofa particle is constrained, excess terms exist using hermitian form of Cartesian momentum pi (I=1,2,3) in usual kinetic energ y (1/2μ) ∑ pi2, and the correct kinetic energy turns out to be (1/2μ) ∑ 1/ fipi fipi, where fi are dummy factors in classical mechanics and nontrivial in quantum mechanics. In this paper the explicit form of the dummy functions fi is given for a charged rigid planar rotator in the uniform magnetic field with different gauge chosen. Under different gauges, we have different sets of dummy factors. It means that these factors do not have direct observable effect.