航海英语船舶浮性资料单项选择题每日一练(2018.10.01)

单项选择题
A current moving across a lock entrance toward the river or toward the dam is called a(n)（）.
A.cutoff
B.outdraft
C.lockwash
D.springpool
单项选择题
For a floating vessel，true mean draft is always the（）.
A.average of the observed drafts
B.draft at the center of flotation
C.draft corresponding to the calculated displacement
D.mean of the calculated drafts
单项选择题
The center of the underwater volume of a floating vessel is the（）.
A.center of buoyancy
B.center of flotation
C.uncorrected height of the center of gravity of the vessel
D.center of gravity of the vessel corrected for free surface effects
单项选择题
In the absence of external forces，the center of buoyancy of an inclined vessel is vertically aligned directly below the（）.
A.center of gravity
B.amidships station
C.center of flotation
D.geometric center of the waterplane area
单项选择题
Reducing the liquid free surfaces in a vessel reduces the（）.
A.roll period
B.metacentric height
C.waterplane area
D.vessel's draft