按要求作图.
(1)如图a所示,工人通过动滑轮拉起重物.请作出工人拉力F的示意图.
(2)如图b所示,一束光平行于凸透镜的主光轴入射.请作出经过凸透镜后的折射光线.
(1)
(2)
“Shall we go fishing this weekend?” “_______. I’ll go with you.”
A.Thank you.
B.I don’t want to go.
C.I have no time
D.That sounds good.
更换规格时带钢等后卷以()带钢入炉前改变速度。
A:低速;
B:高速;
C:平均速度.