题干

1928年,德国物理学家玻特用α粒子轰击轻金属铍时,发现有一种贯穿能力很强的中性射线.查德威克测出了它的速度不到光速的十分之一,否定了是γ射线的看法,他用这种射线与氢核和氮核分别发生碰撞,求出了这种中性粒子的质量,从而发现了中子.

①请写出α粒子轰击铍核( 49Be )得到中子的方程式.

②若中子以速度v0与一质量为mN的静止氮核发生碰撞,测得中子反向弹回的速率为v1,氮核碰后的速率为v2,则中子的质量m等于多少?

上一题 下一题 0.0难度 选择题 更新时间:2019-10-12 10:08:28

答案(点此获取答案解析)

解:① 49Be+24He612

同类题4

阅读理解

    Guide to Stockholm University Library

    Our library offers different types of studying places and provides a good studying environment.

    Zones

    The library is divided into different zones. The upper floor is a quiet zone with over a thousand places for silent reading, and places where you can sit and work with your own computer. The reading places consist mostly of tables and chairs. The ground floor is the zone where you can talk. Here you can find sofas and armchairs for group work.

    Computers

    You can use your own computer to connect to the wifi specially prepared for notebook computers; you can also use library computers, which contain the most commonly used applications, such as Microsoft Office. They are situated in the area known as the Experimental Field on the ground floor.

    Group-study Places

    If you want to discuss freely without disturbing others, you can book a study room or sit at a table on the ground floor. Some study rooms are for 2-3 people and others can hold up to 6-8 people. All rooms are marked on the library maps.

    There are 40 group-study rooms that must be booked via the website. To book, you need an active University account and a valid University card. You can use a room three hours per day, nine hours at most per week.

    Storage of study material

    The library has lockers for students to store course literature. When you have obtained at least 40 credits(学分), you may rent a locker and pay 400 SEK for a year's rental period.

    Rules to be followed

    Mobile phone conversations are not permitted anywhere in the library. Keep your phone on silent as if you were in a lecture and exit the library if you need to receive calls.

    Please note that food and fruit are forbidden in the library, but you are allowed to have drinks and sweets with you.