作者dowdow0728 (火妖貓兒)
看板Physics
標題[問題] 單位
時間Sun Nov 8 17:26:52 2009
The cable of the 1800kf elevator cab snaps
when the cab is at rest at the first floor,
where the cab bottom is a distance d=3.7m
above a spring of spring constant k=0.15
MN/m.
A safety device clamps the cab against guide rails
so that a constant frictional force of 4.4
kN
opposes the cab's motion.
question:Find the Max distance
x that the spring is compressed.
(the frictional force still acts during this compression)
這是Halliday第八版P.195-65
不敢亂翻譯怕誤了原意
我的算法是:
mg(h+x)-(Fk)(h+x)=(1/2)kx^2
但算出來的答案是18.016
跟解答的0.9差了超過20倍
另外，對於單位我也不甚確定
MN 到底是多少N呢?
kN 又是多少哩?
百思不得其解，還望高手解惑!!!
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1F：推 philip0307:M 該不會是指Mega(10^6)吧 XD 11/08 17:31
2F：→ philip0307:如果是的話k就是10^3嚕 科 11/08 17:32
3F：推 ntust661:樓上沒錯@@ 11/08 17:32
4F：→ dowdow0728:喔謝謝!!!!!! 11/08 17:50
5F：→ dowdow0728:帶入正確的單位後算對了!!!(淚眼) 11/08 17:53