单选题Propeller pitch speed minus ship speed divided by the propeller pitch speed is termed （）.A apparent slipB tree slipC pitchD propulsive efficiency

Propeller pitch speed minus ship speed divided by the propeller pitch speed is termed ___.

A.apparent slip

B.true slip

C.pitch

D.propulsive efficiency

In reducing engine speed to an efficient propeller speed by the use of reduction gears, _______.

A.speed and torque are both reduced

B.speed is reduced and torque remains unchanged

C.speed is reduced and torque is increased

D.speed is sometimes unchanged while torque is increased

In moving forward, a ship imparts forward motion to the water at the stems, this is known as _____.

A.the speed of the vessel

B.the speed of the propeller

C.the wake

D.the wake fraction

Compared to a constant pitch propeller, a controllable pitch propeller

A.more efficiently uses available engine power

B.operates at a lower efficiency at a fixed speed

C.produces the same torque at lower engine power

D.develops its rated power at a lower speed

An over-speed safety device is usually fitted to a generator engine for ___ in the event of over-speed.

A.stabilizing the ship speed

B.increasing the fuel pump setting

C.braking the crankshaft

D.cutting power off the engine

A.The automatic control system

B.The speed regularly system

C.The transmission system

D.The compression air system