[领域] 物理 [来源] 考古题 [题目] 第一题 Which of following is correct, (a) the friction of ice on ice depends on both temperature and sliding speed. At low temperature (-40°C), the static coeficient is 0.45 and drops as temperature rises (b) When a bicycle is pedaled the bottom of rear wheel is pushed forward against road (c) The phenomenon of Stick-Slip occurs when the relative speed of the sliding surfaces is high and when one of the objects cannot vibrate (d) force of friction is proportional to load and contact area (e) the force of static friction opposes the tendency of block to move relative to the surfaces. Kinetic friction occurs when both surfaces and block are weIded 第二题 同重量两车，在十秒钟由静止加速，A车可达60公里/小时，B车可达 120小时/公里，B车与A车的输出马力比值为多少？ 第三题 轨道速度 太空中两物体分别以r及4r(距地心距离)轨道绕地球运行，在雷达萤幕上，速度比为多少? --

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