题目内容
电动自行车是目前一种较为时尚的代步工具，某厂生产的一种电动自行车，设计质量(包括人)为m=80kg，动力电源选用能量存储量为“36V10Ah”(即输出电压为36V，工作电流与工作时间的乘积为10安培小时)的蓄电池(不计内阻)，所用电源的额定输出功率P=180W，由于电动机发热造成的损耗(其它损耗不计)，自行车的效率为η=80%。如果自行车在平直公路上行驶时所受阻力跟行驶速率和自行车对地面的压力的乘积成正比，即f=kmgv，其中k=5.0×10 -3 s·m -1 ，g=10m/s 2 ，求： 自行车电动机的内阻为多少？
查看答案
搜索结果不匹配？点我反馈
更多问题
物体A、B的质量相等，把它们加热到相同的温度，然后再把它们分别放入等量、同温度的水里，A物体能使水温升高10℃，B物体能使水温升高20℃，设A的比热为C1，B的比热为C2，则______。
按照设计依据性文件完整性考核标准，不合格的为______ Ⅰ．无上级批准的可行性研究报告或项目任务书 Ⅱ．无设计合同或协议书 Ⅲ．无相关的建设红线图 Ⅳ．无必备的设计依据资料 Ⅴ．无工程地质勘察报告 Ⅵ．无工程概算书
从地面竖直上抛一物体A，同时在离地面某一高度处有另一物体B自由落下，不计空气阻力，两物体在空中同时到达同一高度时速率都为v，下列说法中正确的是______。
Where Did All the Ships GoThe Bermuda Triangle (三角区) is one 1 the greatest mysteries of the sea. In this triangular area between Florida, Puerto Rico and Bermuda in Atlantic, ships and airplanes 2 to disappear more often than in 3 parts of the ocean. And they do so 4 leaving any sign of an accident or any dead bodies.It is 5 that Christopher Columbus was the first person to record strange happenings in the area. His compass stopped working, a flame came down from the sky, and a wave 100 to 200-feet-high carried his ship about a mile away.The most famous disappearance in the Bermuda Triangle was the US Naval (海军的) Air Flight 19. 6 December 5, 1945, five bomber planes carrying 14 men 7 on a training mission from the Florida coast. Later that day, all communications with Flight 19 were lost. They just disappeared without a trace.The next morning, 242 planes and 19 ships took part in the largest air-sea search in history. But they found nothing.Some people blame the disappearances 8 supernatural (超自然的) forces. It is suggested the 9 ships and planes were either transported to other times and places, kidnapped (绑架) by aliens (外星人) 10 attacked by sea creatures.There are 11 natural explanations, though. The US Navy says that the Bermuda Triangle is one of two places on earth 12 a magnetic compass (指南针) points towards true north 13 magnetic north. 14 , planes and ships can lose their way if they don"t make adjustments.The area also has changing weather and is known 15 its high waves. Storms can turn up suddenly and destroy a plane or ship. Fast currents could then sweep away any trace of an accident.
微信支付 
支付宝支付