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【单选题】
凡是在孤立体系中进行的变化,其dU 和dH 的值一定是:A.
dU >0, dH >0
B.
dU =0, dH =0
C.
dU <0, dH <0
D.
dU =0,dH 大于、小于或等于零不能确定。
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【单选题】Running an electric winch at slow speed over a long period of time causes ______．
A.
the speed to be retarded by the friction brake
B.
a load to go downward at full speed
C.
the circuit breaker to turn off
D.
the resistors to overheat and ually burn out
【简答题】女子个人时间为___________。 A、30秒 C、60秒 B、90秒 D、120秒
【单选题】If an electric cargo winch is being used to lift a draft of cargo and the engine room loses all power，which will occur ________．
A.
A pawl，forced by a spring mechanism，will engage the teeth of the bull gear and hold the load
B.
An electromagnetic brake will hold the load where it is suspended
C.
The load will fall rapidly to the deck unless the foot brake is engaged
D.
The load will slowly lower to the deck under control of the drag of the winch motor
【简答题】比一比。 30分○30秒 1时○60秒 60分○1时 1分○61秒
【简答题】80分=（ ）时（ ）分 60秒=（ ）分 1分40秒=（ ）秒
【简答题】我会比．（填“＞”“＜”或“﹦”） 60分______60秒 20分______1时 1分______85秒 60秒______1分 1时______55分 90分______1时．
【单选题】Electric cargo winches have an overload safety device which normally cuts the current to the winch motor（）.
A.
after torque causes line pull to exceed the rated capacity of the winch
B.
before the line pull reaches the rated capacity of the winch
C.
when the line pull reaches the breaking strength of the fall
D.
before the safe working load of the fall is reached
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