(1)答Fn=mv.v/r=20N,G=5N,所以T=Fn-G=15N
(2)最低点Fn=mv^2)/r=40N,T=Fn+G=45N
记住,最高点T=Fn-G,最低点T=Fn+G,其中r=0.4,m=0.5,ev是线速度.