Re: [問題] 兩題物理
※ 引述《freedom76912 (KHAKI)》之銘言：
: 1.two cylinder and rotational inertia about their central axes are supported
: by axles perpendicular to the plane. the large cylinder is initially rotating
: clockwise with angular velocity W. the small cylinder is moved to the right
: until it touches the large cylinder and is caused to rotate by the frictional
: force between the two. eventually, slipping ceases, and the two cylinders
: rotate at constant rates in opposite directions
: A.find the final angular velocity W' of the small cylinder
: B.why does neither angular momentum nor kinetic energy conserve
: (恩...請自己畫兩個圓盤 為 I1 I2 R1 R2)
應該是用衝量矩算:fR=I(dW)/dt 積分後可得fRt=IW 故W的變化量正比於R/I
最後兩盤切線速度相同R1(W-W1)=R2W2 可解得W2=Wf=R1R2W1I1/(R1^2I2+R2^2I1)
我也想知道位啥不能用角動量守衡@@ 有同學能說明一下嗎orz
: 2.the particle of mass m slide down the frictionless surface through height
: h and collide with the uniform vertical rod (mass M rotational inertia I),
: sticking to it. the rod pivots about point O through the angle theta before
: momentarily stopping. find theta.
: (恩...m從一個半徑h的弧形軌道下滑 黏上杆子的末端)
: 沒有圖...sorry
可用能量守衡和對轉軸角動量守衡算:初始轉動動能=達最高點的位能
注意能量守衡中棒子位能要取質心 別忘記質點也有位能
且轉動慣量會改變
答案算出來不怎麼好看...
第一題沒啥把握 有錯請大家指教一下!
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