根据短文回答问题，每空一词。

     My name is Charlie Street. I'm not twelve. I am eleven. I'm not in Grade Eight. I am in Grade Seven.

I'm in Class Two. My teacher isn't Miss Black. My teacher is Mr. Grey. My phone number is 6688469.

1. What is my last name? ______　　

2. How old am I? ______　　

3. What grade am I in? In Grade ______. 　　

4. Who is my teacher? ______ ______. 　　

5. What class am I in? In Class ______.

氢原子中质子不动，电子绕质子做匀速圆周运动的半径为r，电子动量大小mv与半径r的乘积mvr等于，h为普朗克常量．如果把电子换成子绕质子做匀速圆周运动，产子带电量与电子相同、质量约为电子的210倍，子动量大小与半径的乘积也等于，求子的轨道半径。