无粘性土根据土的()进行工程分类，碎石土是指粒径大于2mm的颗粒超过总质量()的土。
参考答案：颗粒级配、50％
The traffic in the town _______be terrible, but now it has improved a lot. I think you will ________it soon.
A. get used to; used to B. get used to; use to C. used to; get used to
一子弹击中木板时的速度是600m/s，历时0.001s 穿出木板，穿出木板时的速度为100m/s，设子弹穿过木板是匀减速运动，试求：
（1）子弹穿过木板时的加速度．
（2）木板的厚度．
