问题
选择题
I went to visit him, I found, _______, that he wasn't at home. [ ]
A. however
B. but
C. and
D. so
答案
答案：A
搜题请搜索小程序“爱下问搜题”
I went to visit him, I found, _______, that he wasn't at home. [ ]
A. however
B. but
C. and
D. so
答案：A
，物块A的质量（包括遮光条）为mA=2.0 kg。开始时在A和B之间压缩一轻弹簧，锁定其处于静止状态，现解除锁定，弹开物块A和B，迅速移去轻弹簧。两物块第一次通过光电门，物块A通过计时器显示的读数t1=9.0×10-4 s，物块B通过计时器显示的读数t2=1.8×10-3 s，重力加速度g取10m／s2，试求：