問
急急急急急..聽日考..
救我...
1.)轉彎果陣可以increase the normzl reaction 黎increase the max. speed
因為the frictional froce is increased..
why true???
2.)normal reaction 係N定R??
3.)
http://lsforum.net/board/attachments/20081127_bbbd7b006b8c6f8e38b5uof1uSKVMF5c.jpg
Fnetradial=N-mg
點解N≠mg
4.)a small object of mass 0.05 kg is released from rest at the rim of a heavy, smooth semi-spherical boel of radius 10cm.Find the force acting on the object by the bowl when it passes the bottom of the bowl
A.0.5N B.1.0N
C.1.5N D.2.0N
[ 本帖最後由 L.K. 於 27-11-2008 18:41 編輯 ] f = u R ma... 但係我覺得INＣＲＥＡＳＥ 個ＭＡＳＳ黎ＩＮＣＲＥＡＳＥ個ＮＯＲＭＡＬ ＲＥＡＣＴＩＯＮ唔可以ＩＮＣＲＥＡＳＥ 個ＭＡＸ ＳＰＥＥＤ．．．
∵friction=mv2/r
cN=mv2/r(c iscoefficient of friction)
cmg=mv2/r
v=√(cgr) 你其實個situation係點?
係平地行定banking先
兩個case 係唔同ga wor 平地........[] for question 3, 如果兩個force balance左, 那佢唔可以轉lor
N-mg = mv^2/r in this case
係top , N+mg = mv^2/r
係中間, 用conservation of energy推公式出來
normal force N 佢個力唔係constant value but係咩令到佢個N>mg[] 因為要有circular motion, 一定要某d 力provide centripetal force for circular motion
其實你gum問法, 係同問物理學家點解會有重力一樣[]
你都可以問, 點解centripetal force 一定要有個力pointed towards the centre acting on the object. 答案最好去宗教討論區求 how about question 1...[] 你自己都prove左條式出來啦
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