作者xgcj (ㄨGc丁)
看板Physics
標題Re: [問題] 角動量的問題
時間Wed Jul 27 00:19:29 2011
※ 引述《bpbpbp (= =)》之銘言：
: A particle of mass M moves in the xy plane. Its coordinates as a function of
: time are given by x(t)=At^3; y(t)=Bt^2-Ct, where A,B,C are constants.
: Find its angular momentum about the origin.
: 答案是 (2C-Bt)MAt^3
: 我想不太通，請版上高手解答。感恩！
→ → → → →
L= x ╳ p =Mx ╳v
→
x= (At^3,Bt^2-Ct,0)
→
v =(3At^2,2Bt-C,0)
→ → → → →
L= x ╳ p =Mx ╳v
=M(0,0,[At^3][2Bt-C]-[Bt^2-Ct][3At^2])
=M(0,0,2ABt^4-ACt^3-3ABt^4+3ACt^3)
=(0,0,MA(2C-Bt)t^3)
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