i did not say there is only 5kg sand on the top -

i did not say there is only 5kg sand on the top -

所有跟贴·加跟贴·新语丝读书论坛

送交者: meiyou 于 2009-11-04, 12:48:28:

回答: 无空气阻力，从机械能守恒看，电子称无法在沙子没落完之前读到5公斤。假由 chouqilozi 于 2009-11-04, 12:33:06:

u can think it is unlimited sand up there

一回事，不过机械能是不守恒的，尘埃落定时转化成热能了，得重来。 (无内容) - chouqilozi (0 bytes) 2009-11-04, 12:58:57 (380587)
- i did not say 机械能守恒 either - if so, sand grain would be bouncing (无内容) - meiyou (0 bytes) 2009-11-04, 13:01:14 (380591)
  - 把这个问题转化成一根绳子下落，交给绳力学专家解决。 (无内容) - chouqilozi (0 bytes) 2009-11-04, 13:55:08 (380608)
    - hehe (无内容) - meiyou (0 bytes) 2009-11-04, 14:04:08 (380609)