[題目] 請問一題普物題目

[chenkaihsu (Shrek)]

[領域] 轉動                            (題目相關領域)

[來源] 課本                            (課本習題、考古題、參考書...)

[題目]A solid uniform disk of mass 21.0 kg  and radius 85.0 cm is at rest flat on a
frictionless surface. The figure  (Intro 1 figure)  shows a view from above.
A string is wrapped around the rim of the disk and a constant force of 35.0
N is applied to the string. The string does not slip on the rim.
When the disk has moved a distance of 5.1 , determine how fast it is moving.

[瓶頸] 我的算法是35*5.1=1/2*21V^2+1/2*IW^2
→70*5.1/15.75=v^2但答案不是這ㄍ
誰可以告訴我哪姐錯了                           (寫寫自己的想法，方便大家為你解答)


--
※ 發信站: 批踢踢實業坊(ptt.cc) 
◆ From: 140.123.222.193
→ chenkaihsu:忘了貼圖...我放在http://www.wretch.cc/album/show.ph
→ chenkaihsu:www.wretch.cc/album/album.php?id=chenkaihsu&book=4
推 EricTao:請愛用  http://0rz.tw/
推 EricTao:轉動的軸一定是質心嗎?
→ a80481ivan:你的W代什麼?不是純滾動  W跟V沒有關係
→ SmArTyau:就你的式子算出的應該會是70*5/26.25=v^2  吧?
→ SmArTyau:                           ^更正為5.1
→ positron:不是純滾動~