# 斜面

## 機械效率

${\displaystyle \mathbf {r} _{A}=R(\cos \theta ,\sin \theta )}$

${\displaystyle \mathbf {v} _{A}=v_{A}(\cos \theta ,\sin \theta ).}$

${\displaystyle P_{\mathrm {in} }=fv_{A}}$

${\displaystyle P_{\mathrm {out} }=\mathbf {W} \cdot \mathbf {v} _{A}=(0,W)\cdot v_{A}(\cos \theta ,\sin \theta )=Wv_{A}\sin \theta }$

${\displaystyle MA={\frac {W}{f}}={\frac {1}{\sin \theta }}}$

${\displaystyle \sin \theta ={\frac {H}{L}}}$

${\displaystyle MA={\frac {W}{f}}={\frac {L}{H}}}$

${\displaystyle MA={\frac {W}{F}}=5}$

## 注释

1. ^

挈：兩輪為高，兩輪為輲，車成梯形也。重其前，弦其前，載弦其前，載弦其軲，而縣重於其前。是梯挈且挈則行。凡重，上弗挈，下弗收，旁弗劫，則下直杝，或害之也流。梯者不得流直也。今也廢尺於平地，重不下，無旁也。若夫繩之引軲也，是猶自舟中引橫也。

——《墨子·经说下》第二八条

## 參考文獻

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9. Dugas, R., A History Of Mechanics, New York: Dover Publications, Inc.: pp. 33–35, 124–126, 1988, ISBN 0-486-65632-2