snowbender 寫:
““Turn skiing” + “buzz words,” not physics. COM—Center of Mass—supposes to be inside the body and moves with body movements, not at the center of the screen as the clip depicted, @0:13~0:22. I saw at epicski, there's also a clip showing the same problem, wonder who is copying who.”
“COM—Center of Mass—supposes to be inside the body and moves with body movements, not at the center of the screen as the clip depicted, @0:13~0:22.”
As a technical discussion, you can either prove your ill-statement, or disprove mine, but you little knowledge have no scientific discipline, you cannot do neither, and you can only continue“whine like a little girl who cannot do her homeworks.” The joke is on you.
You're welcome to revisit the whole thread to see how you denied all the proofs. And to put a nail into your coffin, let see what your beloved Bob Barnes said about COM.
If you need any further proof, go talk to Bob Barnes, or your Physics professor in your Taiwan university, or any Physics text book.
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Center of Mass
Commonly abbreviated "CM" (or "CG" for center of gravity), this is the point at which all the mass of an object or system of objects acts as if it were concentrated, and around which an object spinning freely through space will rotate. For all practical (skiing) purposes, the term is equivalent to and interchangeable with "center of gravity."
A very important (and commonly misunderstood) point about center of mass: it is "mobile"—it is not located in a particular part of the body like an organ. It moves within—and sometimes outside of—the body with changes of body position. In particular, it is not the same as, or necessarily in the same place as, the hips.
CM moves about with varying body positions—it is a dangerous oversimplification to equate it with "hips."
Misunderstanding of center of mass commonly causes critical errors in movement analysis—particularly when assessing balance and stance issues and fore-aft pressure. Instructors—be sure you've got this right!
#286 回覆: 回复: 回覆: 回复: 回覆: 太極荒島
發表於 : 週四 2月 11, 2016 3:19 pm
由 beg
B2L2 寫:You're welcome to revisit the whole thread to see how you denied all the proofs. And to put a nail into your coffin, let see what your beloved Bob Barnes said about COM.
If you need any further proof, go talk to Bob Barnes, or your Physics professor in your Taiwan university, or any Physics text book.
-----------------------------------
Center of Mass
Commonly abbreviated "CM" (or "CG" for center of gravity), this is the point at which all the mass of an object or system of objects acts as if it were concentrated, and around which an object spinning freely through space will rotate. For all practical (skiing) purposes, the term is equivalent to and interchangeable with "center of gravity."
A very important (and commonly misunderstood) point about center of mass: it is "mobile"—it is not located in a particular part of the body like an organ. It moves within—and sometimes outside of—the body with changes of body position. In particular, it is not the same as, or necessarily in the same place as, the hips.
CM moves about with varying body positions—it is a dangerous oversimplification to equate it with "hips."
Misunderstanding of center of mass commonly causes critical errors in movement analysis—particularly when assessing balance and stance issues and fore-aft pressure. Instructors—be sure you've got this right!
B2L2 寫:You're welcome to revisit the whole thread to see how you denied all the proofs. And to put a nail into your coffin, let see what your beloved Bob Barnes said about COM.
If you need any further proof, go talk to Bob Barnes, or your Physics professor in your Taiwan university, or any Physics text book.
-----------------------------------
Center of Mass
Commonly abbreviated "CM" (or "CG" for center of gravity), this is the point at which all the mass of an object or system of objects acts as if it were concentrated, and around which an object spinning freely through space will rotate. For all practical (skiing) purposes, the term is equivalent to and interchangeable with "center of gravity."
A very important (and commonly misunderstood) point about center of mass: it is "mobile"—it is not located in a particular part of the body like an organ. It moves within—and sometimes outside of—the body with changes of body position. In particular, it is not the same as, or necessarily in the same place as, the hips.
CM moves about with varying body positions—it is a dangerous oversimplification to equate it with "hips."
Misunderstanding of center of mass commonly causes critical errors in movement analysis—particularly when assessing balance and stance issues and fore-aft pressure. Instructors—be sure you've got this right!
I respect Bob Barnes as you gappers’ leader, but not his “physics” knowledge. What he said is correct: “Commonly abbreviated "CM" (or "CG" for center of gravity), this is the point at which all the mass of an object or system of objects acts as if it were concentrated, and around which an object spinning freely through space will rotate.” Nevertheless, what he didn’t account for is that when body parts move, the CG within the body moves as well, i.e. CG is not “stationary,” so his “stationary” CG in space conclusion is wrong, as the body he showed cannot be “spinning freely” in space. “外行人，外行話”‧
And it doesn’t matter what the body shape is,“a body always fall with its CG,”
snowbender 寫:I respect Bob Barnes as you gappers’ leader, but not his “physics” knowledge. What he said is correct: “Commonly abbreviated "CM" (or "CG" for center of gravity), this is the point at which all the mass of an object or system of objects acts as if it were concentrated, and around which an object spinning freely through space will rotate.” Nevertheless, what he didn’t account for is that when body parts move, the CG within the body moves as well, i.e. CG is not “stationary,” so his “stationary” CG in space conclusion is wrong, as the body he showed cannot be “spinning freely” in space. “外行人，外行話”‧
And it doesn’t matter what the body shape is,“a body always fall with its CG,”
Funny why you are so proud of yourself and claimed the leader of gappers' leader pride about your skiing. I remember you call him a true master that time.
小女孩真的要多讀書學好英語，人家說 "mobile" 你就説成 "stationary"，真怪。
重點又不是討論CG是否move，係可否離身嗎，跟著又是不知所為 post 個 wrong clip 就又算了。來來去去，左右逃跑。
你話BB的 physics 太差，那他們的 physics 又可不可以？好可能想當年，你的 professor 都是用他們的書來教你
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"The centre of mass of an object need not lie within the object.There is no dough at the centre of mass of a doughnut,and no iron at the centre of mass of a horseshoe."
Source(s): Fundamentals Of Physics - David Halliday,Robert Resnick,Jearl Walker.
#298 回覆: 太極荒島
發表於 : 週六 2月 13, 2016 8:56 pm
由 snowbender
pku 寫:眼高手低，你講你自己，你連在一般的饅頭也不能用短彎連續滑十個，
才說過，“新雪好滑”！像你滑的雪況，我可以“跟”你“turn for turn.” 要不要算算下面影片裡有几個彎？
