定轴转动刚体上受碰撞力作用,为什么轴承处也会产生碰撞力?如果转轴恰好通过刚体的质心,能否找到撞击中心?
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什么是主振动?两个主振动的合成是否为简谐振动?是否是周期运动?
A.Algebra and math. B.English-language arts and mathematics. C.Math and
Algebra and math.
B. English-language arts and mathematics.
C. Math and reading.
D. English and reading.
5,10,20,30,()
A. 40
B. 45
C. 50
D. 60
A.Study for some profession.B.Attend a medical school. C.Stay in busines
A. Study for some profession.
B. Attend a medical school.
C. Stay in business.
D. Sell his shop.