2020－2022八上英语周报外研答案

13.(6分)(1)使细绳的拉力为小车做匀加速运动的合外力(1分)需要(1分)(2)2.0(2分)(3)偏小(2分)【解析】(1)本实验使用了拉力传感器,实验时需要适当拍高长木板的右端以平衡摩擦力,其目的是使细绳的拉力为小车做匀加速运动的外力中衡哪擦力时,小车需要连接纸带,因为小车连接纸带运动时带与打时器之间也存在阻力。(2)每相邻的两计数点间都有四个点未画出,困此计数点之间的时间间隔为7=0.1s,根据△=ar,代入数后解合10.61+8.61-6.59-4.61×10-m/s2=2.0m/s2。47.4×0.12(3)观察题图丙可知,当细绳上的拉力达到一定值时,小车才有加速度,这说明平衡摩擦力不足,长木板的倾角偏小。

One possible versionSeveral minutes later, the ice broke suddenly and Harry's feet sank into the water. It was noep, but his legs got wet to the knees. Harry was so upset that the accident would delay hisschedule. He had to find some firewood to build a fire to dry his clothes. He pulled off his glovestook out his matches, and lighted the fire. Seeing the burning fire, he had thought he was safe. Butsuddenly, without warming, a heavy mass of snow dropped down. The flame of hope was put outUnluckily, his dog ran away and the fear of death came over Harry. He had no choice but torun to save himself. However, he did not feel his feet when they hit the ground. Having falleneveral times, he decided to rest a while. As he lay in the snow, he noticed he was not shaking. Hecould not feel his nose or fingers or feet. A feeling of horror came into his mind. It was when herealized he was going to die that he heard a bark and the noise his friends made

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