若$\sqrt{95-n}$是整数，则自然数n的值有（　　）个．

如图所示，间距为d的平行金属板间电压恒定．初速度为零的电子经电压U₀加速后，沿两板间的中心线进入板间电场，电子恰好从下极板边缘飞出，飞出时速度的偏向角为θ．已知电子质量为m，电荷量为e，电子重力不计，求：

    Good habits are important to us. We should build good living habits. Now let's have a look at the two brothers. Li Qiang and Li Gang are brothers. But their living habits are different. Now let's go to Li Qiang's room. Li Qiang cleans his bedroom every day and puts his things away. Look! There is a computer on the desk. There are two balls under the bed. A guitar and a kite are on the wall. Some books are on the shelf. So he must be a careful boy. Now let's go to Li Gang's room. The room is not clean. Can we see his clothes on the desk? Oh, yes. We can see a football and a knife on the desk, too. Li Gang never does any cleaning on weekends. So his room is in a mess.

    What do you think of Li Qiang and Li Gang? Li Qiang is a good boy. Li Gang must learn from his brother