[課業] 材力機設問題
小弟正自學材力，但搞不懂為何此題第二張圖畫紅線及手指區域的tau是為負的，與扭轉
方向有關?想請問扭轉剪應力判斷正負的方法?
http://i.imgur.com/nKESeBC.jpg
我有大概goo了一下順逆時針正負(寫在第二張圖)，因為碰到另一題類似的發現第三張圖
的題目解答他卻是取正的?
麻煩版上高手解惑了 感謝!
--
Sent from my Android
--
※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 111.70.104.228
※ 文章網址: https://www.ptt.cc/bbs/Examination/M.1434438864.A.720.html
→
06/16 15:21, , 1F
06/16 15:21, 1F
→
06/16 15:21, , 2F
06/16 15:21, 2F
→
06/16 16:07, , 3F
06/16 16:07, 3F
→
06/16 16:09, , 4F
06/16 16:09, 4F
→
06/16 16:11, , 5F
06/16 16:11, 5F
→
06/16 16:12, , 6F
06/16 16:12, 6F
→
06/16 16:14, , 7F
06/16 16:14, 7F
→
06/16 16:16, , 8F
06/16 16:16, 8F
推
06/16 16:20, , 9F
06/16 16:20, 9F
→
06/16 16:49, , 10F
06/16 16:49, 10F
→
06/16 18:04, , 11F
06/16 18:04, 11F
→
06/16 18:42, , 12F
06/16 18:42, 12F
推
06/18 18:16, , 13F
06/18 18:16, 13F
推
06/27 00:17, , 14F
06/27 00:17, 14F