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标题：全部的人請進。特別是物理系的
1楼
法拉利 发表于：2004-12-17 9:35:25幫我做幾道物理題目。求求你。。。跪拜﹑﹑﹑﹑
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第1道﹕重量1200KG的車在平路上行駛10m/s。輪胎和路的阻力比率是0。51。請問汽車的輪子的半徑至少是多少﹖﹖
第2道﹕一個重100N的物體被替換成200N的物體﹐然後向地球外心移動2倍的距離﹐求新的重量= =
英文版﹕ an object with weight of 100N is replaced by a 200N weight then move twice as far from the earth, waht is the weight at this new location??
第3題﹐第1問.a flat turntable is accelerated from 0 to 20 rad/sec in 10 seconds. The turntable has a mass of 5KG and a radius of 0.25 meters. what is the angular acceleration???(answer by r/s^2)
第2問﹕what is the moment of interia of the turntable from the problem above??
第3問﹕what is the torque needed to accelerated the turntable??
第4題﹕what is the energy needed to accerlate the turntable
第5題﹕once up to speed, a 1kg weight is stuck to the outside edge of the moving turntable, what will its new angular velocity be??
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第1道﹕重量1200KG的車在平路上行駛10m/s。輪胎和路的阻力比率是0。51。請問汽車的輪子的半徑至少是多少﹖﹖
第2道﹕一個重100N的物體被替換成200N的物體﹐然後向地球外心移動2倍的距離﹐求新的重量= =
英文版﹕ an object with weight of 100N is replaced by a 200N weight then move twice as far from the earth, waht is the weight at this new location??
第3題﹐第1問.a flat turntable is accelerated from 0 to 20 rad/sec in 10 seconds. The turntable has a mass of 5KG and a radius of 0.25 meters. what is the angular acceleration???(answer by r/s^2)
第2問﹕what is the moment of interia of the turntable from the problem above??
第3問﹕what is the torque needed to accelerated the turntable??
第4題﹕what is the energy needed to accerlate the turntable
第5題﹕once up to speed, a 1kg weight is stuck to the outside edge of the moving turntable, what will its new angular velocity be??
2楼
法拉利 发表于：2004-12-17 9:52:53
繼續﹕如圖。A load hangs from the end of a crane that has a support cable attached 1/2 way on the boom as shown, find T in terms of L.
a disc is released and falls as it unwinds a rope around its edge
求﹕
a) time to fall 5 meters
b) angular acceleration
c)linear acceleration
d)torque on the disk
e)tension in the rope.
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繼續﹕
a disc and a hop race down the ramp, the angle of the ramp is 20degrees, length is 2m. find the time between the winner and the loser.no friction
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完
請巴怎麼做的也打出來吧。。
求求你們了拉。。。
我慘了
3楼
joe_xz 发表于：2004-12-17 10:39:20楼上翻译成中文行不？英文看着太累。
还有，阻力比率是什么？
那两张图也看不清楚
还有，阻力比率是什么？
那两张图也看不清楚
4楼
joe_xz 发表于：2004-12-17 10:47:14第2题：F=GMm/r^2
所以r变为2倍，F变为1/4，新的重量是50N
不过不太明白前面的替换物体有什么意义
所以r变为2倍，F变为1/4，新的重量是50N
不过不太明白前面的替换物体有什么意义
5楼
法拉利 发表于：2004-12-17 11:46:381)一個圓盤加速0到20rad/sec 在10秒內。圓盤中5KG﹐半徑0。25M。求ANGULAR ACCERATION。
2)這題的MOMENT OF INTERTIA士多少﹖﹖(就是I)
3)需要多少TORQUE持續﹖
4)需要多少芰?/P>
5)如果在圓盤的外面加1KG的量﹐求ANGULAR VELOCITY﹖﹖(R/S)
2)這題的MOMENT OF INTERTIA士多少﹖﹖(就是I)
3)需要多少TORQUE持續﹖
4)需要多少芰?/P>
5)如果在圓盤的外面加1KG的量﹐求ANGULAR VELOCITY﹖﹖(R/S)
6楼
joe_xz 发表于：2004-12-17 12:21:53第3题
1、ANGULAR ACCERATION=20/10=2r/s^2
2、I=mr^2/2
3、M=J*ANGULAR ACCERATION=[(mr^2)/2]*ANGULAR ACCERATION
4、E=(1/2)*J*w^2
5、(1/2)*J*w^2=(1/2)*J*w'^2+(w'*r)^2*m'*(1/2)
1、ANGULAR ACCERATION=20/10=2r/s^2
2、I=mr^2/2
3、M=J*ANGULAR ACCERATION=[(mr^2)/2]*ANGULAR ACCERATION
4、E=(1/2)*J*w^2
5、(1/2)*J*w^2=(1/2)*J*w'^2+(w'*r)^2*m'*(1/2)
7楼
joe_xz 发表于：2004-12-17 12:30:47第一张图那道：
设斜杆长l
L*l*cos30=T*(l/2)*sin80
可求得T
设斜杆长l
L*l*cos30=T*(l/2)*sin80
可求得T
8楼
joe_xz 发表于：2004-12-17 12:58:54第二张图用能量守恒
(1/2)Jw^2+(1/2)mv^2=mgh
v=wr
(1/2)Jw^2+(1/2)mv^2=mgh
v=wr
9楼
法拉利 发表于：2004-12-17 13:41:09請大家繼續= =
謝謝了。鞠躬
謝謝了。鞠躬
10楼
xiabingg 发表于：2004-12-17 16:25:05楼上大个是?