英语周报 2018-2022 八年级 新 2答案

11【解析】(1)设细线aO上的拉力为T,则有2Tcos30°=Fo(2分解得T=20N(2分)重物A的质量mA==2(2分(2)对结点O由平衡条件得细线cO上的拉力F1=Tcos60°=10N.(2分)mcg=FI=10 N(2分)解得mc=1kg(2分)细线b的拉力F2=Tsin60°=103N(2分)根据平衡条件知桌面对物块B的摩擦力f=F2=103N(2分)

第二节One possible versionDiamond hurriedly ran to the bird. Approaching thebird. he ran around themelt the bird. and thenbarked at his master. Gunnar understood the boy was asking him to help the bird. So, he picked it up gently. Aftercareful examination, Gunnar told his boy that Bibi didn'tlf indoors Considering that the bird wasn't wellgH to leave, he put him back in the basket, with andded bite of sweet potato as well. He decided to set himfree the next day, when he would be fully recoveredAfter Bibi s recovery, Gunnar placed him back out onthe balcony. Suddenly, the bird started to sing, as if hewere expressing thanks to Diamond. Then he spread hiswings,flying away. A while after the bird had gone, Isaid to Diamond: Where is Bibi?'"recalled GunnarHe looked at me, very sharply, then jumped on the sofaand ran directly to the balcony door. He knew exactly whatI was talking about.

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