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【单选题】
我国航天运载火箭领域,多数长征系列运载火箭采用气瓶为( )
A.
高温 MG7ELI 镁合金气瓶
B.
低温 MG7ELI 镁合金气瓶
C.
高温 TA7ELI 钛合金气瓶
D.
低温 TA7ELI 钛合金气瓶
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【判断题】在同一品种石油沥青材料中随着牌号增加,沥青黏性增加(减小),塑性增加,而温度敏感性减小
A.
正确
B.
错误
【单选题】下面不是位元件的是( )
A.
X
B.
Y
C.
M
D.
D
【单选题】下列工件定位面与定位元件不是限制三个自由度的是:( ACE )
A.
外圆柱面与长 V 型铁
B.
圆锥孔与固定顶尖
C.
圆柱孔与短圆柱销
D.
圆柱孔与固定锥销
【判断题】在同一品种石油沥青材料中,牌号愈小,沥青愈软;随着牌号增加,沥青黏性增加,塑性增加,而温度敏感性减小。()
A.
正确
B.
错误
【单选题】When acceleration is _______, a velocity of a particle is constant.
A.
Constant but non zero
B.
Maximum
C.
Zero
D.
None of the above
【简答题】3-2Translation: Newton’s second law implies that: When a body is acted upon by a constant force, its resulting acceleration is inversely proportional to the mass of the body and is directly proportion...
【单选题】下面不是位元件的是( )。
A.
X
B.
Y
C.
S
D.
D
【判断题】When a body oscillating on a horizontal spring passes through its equiibrium position, its acceleration is zero. When the bob of an oscillationg simple pendulum passes through its equilibrium position...
A.
正确
B.
错误
【单选题】The magnitude of the normal acceleration is
A.
proportional to radius of curvature.
B.
inversely proportional to radius of curvature.
C.
sometimes negative.
D.
zero when velocity is constant.
【单选题】When acceleration is _______, a velocity of a particle is constant.
A.
Constant but non zero
B.
Maximum
C.
Zero
D.
None of these choices
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