作者dargonma (dargon)
站内Physics
标题Re: [题目] 有关於摩擦和功率的问题
时间Thu Mar 6 20:15:39 2008
※ 引述《taigoinwo (还是一只幼鼠)》之铭言：
: [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？
如果这两车都是做等加速度且输出马力跟加速度成正比的话
应该用v=at就可以解了吧
: 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?
这一题我是用GMm/r^2=mv^2/r来看的
算出来是2:1
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