问题
单项选择题
由一个定滑轮和一个动滑轮组成的滑轮组吊装一个物体,由定滑轮引出端的拉力为重物的()。
A、1/2
B、1/4
C、2/3
D、相等
答案
参考答案:A
由一个定滑轮和一个动滑轮组成的滑轮组吊装一个物体,由定滑轮引出端的拉力为重物的()。
A、1/2
B、1/4
C、2/3
D、相等
参考答案:A
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Some parents like to 2 birthday parties for their children. If they keep on doing this, their children will think it 3 for them to enjoy birthday parties every year. Year after year, maybe they will forget their 4 birthdays and only remember their own. It is against traditional habits. Many parents don’t let the children do housework. They think children have only one thing to do. They should study hard and do 5 in their lessons. If parents go on doing this, the children will only learn to open their mouths to be fed and stretch out (伸出) their arms to be 6 every day. When the children grow 7 , they will be able to do 8 , and they won’t even find a job. Parents should teach the children 9 to do housework because it can help them start good 10 of working by themselves. |