中国大学MOOC: http://edu-image.nosdn.127.net/F43D2B8BF6208372FA3F9486D534C5EB.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100求BD杆件的内力，可以截断BD,采用虚速度法，D点的虚速度垂直与BD.
举一反三
- 中国大学MOOC: 如图所示，网孔I的网孔电流法方程应为（ ）http://edu-image.nosdn.127.net/38E38CF64EC070E95E47B1FB7F977634.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100http://edu-image.nosdn.127.net/43A73C3A226230A96E5C62EDD9D4EBE8.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100
- [img src="http://edu-image.nosdn.127.net/C8EC0B0C890042F81AB9CF0941243122.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"] 未知类型：{'options': ['2', '0', '1', '[img src="http://edu-image.nosdn.127.net/EAB437E744FF87F763873F106CCCE3E9.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]'], 'type': 102}
- [img src="http://edu-image.nosdn.127.net/E9ECD91FC8FB3437CBAE9E731E05C1F9.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"] 未知类型：{'options': ['[img src="http://edu-image.nosdn.127.net/844D4F13280FCB22936CC001C2655964.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]', '0', '1', '[img src="http://edu-image.nosdn.127.net/39355C3F2BE9AE15346505596CAABAF4.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]'], 'type': 102}
- [img src="http://edu-image.nosdn.127.net/61AE584E303C1B2E4BAC078E8F1001DF.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"] 未知类型：{'options': ['[img src="http://edu-image.nosdn.127.net/130A64ABA6A61E687A5F469C34143002.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]', '[img src="http://edu-image.nosdn.127.net/20F7AE0D2D61D3B7C77AC42946420A5E.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]', '', '[img src="http://edu-image.nosdn.127.net/EA9E8710C7E7C6FB3911A4B2C566E8FF.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]'], 'type': 102}
- [img src="http://edu-image.nosdn.127.net/1D264CE1268E417C9F892050434EFC44.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"] 未知类型：{'options': ['[img src="http://edu-image.nosdn.127.net/703D93736FA0EE8E801533F7F6880BBA.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]', '[img src="http://edu-image.nosdn.127.net/F5B2914EB077712BB840150D7DF6F15C.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]', '负惯性指数为零', '[img src="http://edu-image.nosdn.127.net/9997728AAB3A20D833FE0662B463B041.bmp?imageView&type=jpeg&thumbnail=890x0&quality=100"]'], 'type': 102}