British Museum Visitor Regulations

    We warmly welcome you on your visit to the Museum. In the interests of the security of all of our visitors we require you follow these Visitor Regulations.

    Admission

    Admission to the Museum is free, but we may charge for entry to some temporary exhibitions and events.

    Opening hours

    We open the Museum's galleries daily from 10:00 am until 17:30 pm. We keep selected galleries open until 20:30 pm on Fridays.

    The Museum's Great Court is open from 9:00 am until 18:00 pm; except on Fridays when it remains open until 20：30 pm.

    You may be asked by your staff to begin leaving up to ten minutes before closing time.

    The Museum is closed 24 -26 December and l January.

    Food and drink

    You aren't allowed to consume food and drink inside the Museum, except in places such as the restaurant and cafes or the forecourt. Families with children may use the Ford Centre for young visitors in the basement of the Museum's Great Court at weekends and during school holidays.

    Animals

    If you have a disability, you may be accompanied in the Museum by your guide, assistant or companion animal. You aren't allowed to bring animals into the Museum under any other circumstance.

    Film, photography and audio（声音的）recording

    Except the place that are indicated by notices, you' re permitted to use hand- held cameras (including mobile phones) with flash bulbs or flash units, and audio and film recording equipment not requiring a stand. You may use your photographs, film and audio recordings only for your own private and non-commercial purposes.

将一定量的人的血液放入装有少量抗凝剂的试管中，静置一段时间后，血液会有明显的分层现象：上层是淡黄色、半透明的____，下层是深红色、不透明的____，上下两层交界处有很薄的一层白色物质是白细胞和血小板．

如图所示，将一块重为3N，体积为100cm³的石块，用细线系着浸没在装有水的圆柱形容器中，容器中水的深度由10cm上升到12cm（容器的重力和容器壁的厚度忽略不计，g=10N/Kg）。求：

⑴石块的质量是多少？
⑵石块的密度是多少？
⑶石块所受的浮力是多少？
⑷容器中水所受到的重力？