阅读理解。

     Harry likes talking too much. His father doesn't like him talking at table. One day at dinner,

     Harry is ready to say something, but his father stops him.

     After a while, they almost finish their dinner. Father asks,"Hi, my boy, what are you going

to say?"

     "Dad, is a fly delicious?" says Harry. "Of course not," says his father. "Why do you ask me that?"

    "A fly was in your bowl just now and you swallowed(吞)it,"says Harry. "Why didn't you

tell me earlier?"

     "You stopped me!"

( )1. At dinner a fly was in Harry's father's bowl.          

( )2. Harry likes talking only at table.                      

( )3. Harry asked his father if a fly was delicious.          

( )4. His father likes eating flies.                          

( )5. Finally, his father knew he ate a fly and was very happy.

如图所示，一质量为M=2kg的绝缘滑板静止于水平面上，它与水平面闻的动摩擦因数为=0.1，绝缘滑板上表面0点的左侧是光滑的，O点的右侧是粗糙的。有质量均为m="1" kg的小物块a、b分别静止地放于绝缘滑板的A点和O点，且A点与O点的间距L="0.5" m，小物块a、b均可视为质点，它们在O点右侧时与绝缘滑板间动摩擦因数均为弘- -整个装置所在空间存在着E=8×l03 N/C且方向水平向右的匀强电场，小物块a带有q=5×10^-4C的正电荷，b和滑板均不带电。若小物块在运动过程中电荷量始终不变，a与b相碰后粘合在一起且碰撞时间极短，小物块恰好能到达绝缘滑板的右端；最大静摩擦力在大小上等于滑动摩擦力，g取10m／s²。求：

（1）小物块a到达O点时的速度。 

（2）绝缘滑板的长度。