算出体积：π（d/2）^2*6*10^(-3)（立方米）然后乘以铜的密度已知铜的密度为8900千克每立方米所以重量为：π（d/2）^2*6*10^(-3)*8900=π（d/2）^2*6*8.9=π*0.35*0.35*6*8.9=6.5415π=20.54031
