问题 问答题

如图1-3-17所示,小车上固定着一根弯成α角的曲杆,杆的另一端固定一个质量为m的球,小车在水平面上做匀速直线运动.分析杆对球的弹力大小和方向.

图1-3-17

答案

杆对球的弹力大小为mg,方向竖直向上.

由于球处于平衡状态,根据二力平衡的条件知,杆对球的弹力方向跟重力方向相反,竖直向上,弹力大小跟球的重力大小相等,等于mg.

听力题

单词拼写(共15小题,每小题1分,共15分)

小题1:Buildingtheproposednewroadwould be __________(环境)damaging,which made the public very concerned.

小题2:The Prime Minister, ___________(陪同)by the governor, led the President up to the house.

小题3:Mr. Liu is a strong supporter who __________(提倡)banning students from using cell phones in the schoolyard.

小题4:We need to take ___________(责任)for looking after our own health; because without it, we can do nothing.

小题5:The stockmarkethas a risk,Youhadbetterget___________(职业)advicebeforebuyingstocks.

小题6:Everydaythey are talkingaboutpeacebut a__________ preparing for war.

小题7:Those close to him are convinced that he has every i__________ of staying on until the end of his second term.

小题8:Sometimes people find it may bepossible to m__________the value of materialgoods in terms of money, but it is extremelydifficulttoestimate the truevalue of them.

小题9:The teacher examined the students on the p__________ lesson, and he was satisfied with what they had done.

小题10:Our teacher often told us meaningfully, “Difficulties s_______ the mind, as labor does the body.”

小题11:A__________ sensitive to criticism, the bull forgot all about the matador and charged at the drunk.

小题12:Though he managed to take a number of b__________ photographs, he could not stay near the volcano for very long.

小题13:After having been i__________ to drive out of town, I began to acquire confidence.

小题14:A colony of bees had turned the engine into a hive and it was totally p__________ in beeswax.

小题15:The plane wasn’t too badly damaged, but over the years, the crash was forgotten and the wreck remained u__________.

填空题