  We explore the relation between black hole mass ($M_{\rm BH}$) and the motion
of the jet components for a sample of blazars. The Very Long Baseline Array
(VLBA) 2cm Survey and its continuation: Monitoring of Jets in active galactic
nuclei (AGNs) with VLBA Experiments (MOJAVE) have observed 278 radio-loud AGNs,
of which 146 blazars have reliable measurements on their apparent velocities of
jet components. We calculate the minimal Lorentz factors for these sources from
their measured apparent velocities, and their black hole masses are estimated
with their broad-line widths. A significant intrinsic correlation is found
between black hole masses and the minimal Lorentz factors of the jet
components, which the Eddington ratio is only weakly correlated with the
minimal Lorentz factor, which may imply that the Blandford-Znajek (BZ)
mechanism may dominate over the Blandford-Payne (BP) mechanism for the jet
acceleration (at least) in blazars.
