一道大學物理題..關于轉(zhuǎn)動慣量的..
將一個40cmX40cm的正方形油畫用一個釘子固定它的住左下角.然后松手--------這個時候,油畫會在重力的作用下,繞著釘子旋轉(zhuǎn)..求：當油畫的質(zhì)心到達釘子的正下方時,油畫轉(zhuǎn)動的角速度.誰能幫個忙啊..我算了好久都沒算對..正確答案是5.3 m/s,但是誰能告訴我這個答案是怎么算出來的- -....
附：原題(翻以前)是這樣的:An enthusiastic physics student mounts on her wall a portrait of her favorite physicist.Her roommate needs tacks to put up photos of David Bowie,and when there is only one tack left,in the lower left corner,gravity causes the portrait to rotate freely around that remaining tack.Assume that the portrait is a square 40 cm on a side.(c) Use energy ideas to determine the velocity of the portrait's center when it has reached a position directly beneath the tack.