混合式碾米机采用混合碾白原理,碾辊为()。
参考答案:砂辊
If you meet your teacher at 7 a. m, what do you say to him or her?[ ]
A. Good morning.
B. Good afternoon.
C. Good evening.
D. Good night.
大小不同的三个力同时作用在一个小球上,以下各组中可使小球平衡的是( )
A.2 N,3 N,6 N
B.1 N,4 N,6 N
C.35 N,15 N,25 N
D.5 N,15 N,25 N