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  大一物理题.Auniformsteelrodoflength1.20mandmassof6.40kghasattachedtoeachendasmallballofmass1.06kg.Therodisconstrainedtorotateinahorizontalplaneaboutaverticalaxisthroughitsmidpoint.Atacertaininstantitis

  大一物理题.

  Auniformsteelrodoflength1.20mandmassof6.40kghasattachedtoeachendasmallballofmass

  1.06kg.Therodisconstrainedtorotateinahorizontalplaneaboutaverticalaxisthroughitsmidpoint.

  Atacertaininstantitisobservedtoberotatingwithanangularspeedof39.0rev/s.Becauseofaxle

  frictionitcomestorest32.0slater.Assumeaconstantfrictionaltorque.

  (a)Findtheangularacceleration.

  (b)Calculatetheretardingtorqueexertedbyaxlefriction.

  (c)Determinethetotalworkdonebytheaxlefriction.

  (d)Calculatethenumberofrevolutionsexecutedduringthe32.0s.

  (e)Nowsupposethatthefrictionaltorqueisknownnottobeconstant.which,ifany,ofthequantitiesabcdordcanstillbecomputedwithoutrequiringanyadditionalinformation?ifanyexistsgiveitsvalue

1回答
2019-05-24 17:55
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唐获

  第一个

  设杆的转动惯量为I1球的为I2

  杆的转动惯量为I1=m1L^2/12球的为m2(L/2)^2*2=m2L^2/2

  因为(I1+I2)α=T

  T=F*L/2*2=FL

  可以解出α

  第二个

  冲量矩等于角动量

  因此(I1+I2)ω=FLt

  第三个

  W=(I1+I2)ω^2/2

  第四个

  W=FS解出S

  revolution=S/2πr

  第五个

  需要知道摩擦力和时间的函数关系.

2019-05-24 17:56:45

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