當踢一個足球到牆的時侯,本身個足球有momentum,但係撞完個牆之後就停左,咁樣睇落去,momentum好似唔conserve,但係本書有話係conserve,為什麼?同地球mass大,v細有關?
2007-03-04 07:24:15 · 3 個解答 · 發問者 2003 2 in 科學 ➔ 其他：科學
你講啱咗,我好sure你本書錯咗,Ken Chan教過由於淨力唔=零(足球和目標在,碰撞後均停止不動)
由於淨力唔=零
地球施予目標的力
整個系統的momentum(i.e.足球+目標)唔conserve
至於地球mass大細已經無關,只要推斷出淨力唔=零,momentum就唔conserve。
要momentum conserve 就要考慮晒足球,目標(牆)和地球。
唔明嘅話再問過,我會盡量回答
2007-03-04 15:57:41 補充：
要考慮momentum conserve唔conserve唔係考慮mass而係淨力=唔=零
2007-03-04 10:55:00 · answer #1 · answered by ? 3 · 0⤊ 0⤋
我都係ken chan的學生
今日岩岩教完conserve -V-
2007-03-17 17:47:16 · answer #2 · answered by Natalie 2 · 0⤊ 0⤋
The momentum of the ball has been transfered to the earth.
m.v = MV
where m and M are the massess of the ball and earth respectively
v is the velocity of the ball before striking the wall
V is the velocity gained by the earth after stopping the ball
thus, V = m.v/M = (m/M)v
since M is very very large as compared with m, V is practically small and which is not observable
2007-03-04 09:27:50 · answer #3 · answered by 天同 7 · 0⤊ 0⤋