Re: [問題] 高中力學
看板Physics作者Emcc (mass, momentum, energy)時間13年前 (2010/12/18 02:09)推噓5(5推 0噓 41→)留言46則, 7人參與討論串6/10 (看更多)
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^^^^^^^^^^^^^^^^^^
你這句話錯了
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你上面推文說
被動輪等速度運動(ie.等角速度轉動)
合力 和 合力矩 都要為零對吧?
如果車輪和軌道間有摩擦
合力矩就不會為零了 --> 所以你得到 "等速度運動的被動輪一定不可能有摩擦力"
但你有沒有想過
摩擦力只會產生在輪子與軌道間嗎
如果輪軸也有摩擦呢? (事實上一定會有的 而且還不小 不然幹嘛發明"軸承")
輪軸摩擦力造成的力矩
能不能和地面摩擦力造成的力矩抵銷
讓合力矩為零呢?
然後車輪還是很乖地作它的 等速度(等角速度)運動 呢?
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