5. A particle of mass m travels in a horizontal circle on a frictionless table. The centripetal force is provided by a string, attached to two bodies of equal mass M, which passes through a hole in the table. The radius of the circle is r. If one of the hanging masses is removed, the new radius will be ______
詳解 (共 1 筆)
助人為本
詳解 #7383780
所以這題用角動量公式即可秒殺
然後要想到角動量L=m*r*v
然後代回向心力公式Fc=m*v^2/r
主要是代v

因為小球質量不變,所以角動量守恆不變
所以向心力和半徑^3成反比
運用這個條件,可以知道向心力和半徑^3相乘為常數
所以假設拿掉質量後為新半徑(r')
