【简答题】在图中,质量为m=12kg、长为l=0.75m的均质杆AB,铰接于固定点A,受到力偶矩M=30N·m的力偶作用,杆的B端与刚性系数k=80N/m的弹簧相连。假设杆从θ 0 =30°时无初速释放,弹簧在杆的初始位置无变形。运动过程中,弹簧借助小轮C保持水平。求当θ=60°时杆的角速度。
【简答题】What is a generally suggested minimum sample size for a group in a causal-comparative study or correlation study?
【单选题】When economists talk about growth in the economy, they measure that growth as the
A.
absolute change in nominal GDP from one period to another.
B.
percentage change in nominal GDP from one period to another.
C.
absolute change in real GDP from one period to another.
D.
percentage change in real GDP from one period to another.
【简答题】Why the manufactures did not accept the new design.
【简答题】一般来讲,谷物中的第一限制性氨基酸为( )。
【单选题】乳中干物质的含量随乳成分的百分含量而变,尤其是()在乳中的变化比较大,因此在实际工作中常用非脂乳固体作为指标。
【判断题】A complete enumeration of the elements of a population or study object is called a sample.