作者EricTao (幻想風)
看板Physics
標題[問題] 一個力學習題
時間Sat Oct 25 22:37:16 2008
這是課本的題目，
A block of mass M is pulled along a horizontal (Fig)
┌──┐ m
frictionless surface by a rope of mass m, as │M ╞══→ F
─┴──┴─────
shown in Fig. A horizontal force F acts on one end
of the rope.
(a) Show that the rope must sag, even if only by
an imperceptible amount. Then, assuming that the
sag is negligible, find --
(b) the acceleration of the rope and the block, --
(c) the force on the block from the rope, and --
(d) the tension in the rope at its midpoint.
看不懂(a)要show繩子會鬆弛(sag)，我不懂為什麼會鬆弛，這樣不就T=0嗎?
還是我誤解了題目的意思?
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 118.166.118.184
1F：推 sukeda:繩子有重量，繩子如果繃緊，將無法有垂直的力抵銷繩重 10/25 22:55
2F：→ EricTao:所以是下垂 而不是鬆弛的意思嗎? 10/25 22:56
3F：推 sukeda:他的鬆弛只是指無法拉直吧 10/25 22:57
4F：→ EricTao:嗯...我查的英漢字典寫鬆弛 讓我會錯意了ˊˋ 10/25 23:03