Physics - Rotation Question with Solution | TestHub

PhysicsRotationCalculation of M.I.Easy2 minPYQ_2020
PhysicsEasysingle choice

A nonuniform rod  OM  of length l has linear mass density that varies with the distance x from left end of the rod according to  λ= λ 0 x 3 L 3 ; Where  λ 0  is constant, is kept along x-axis and is rotating about an axis  AB , which is perpendicular to the rod as shown in the figure. What is the value of x  so that moment of inertia of rod about axis  A I AB  is minimum?

 

Options:

Answer:
D
Solution:

IAB=y2dm=λ03-xl-x(y+x)3y2dy

(y+x)3y2dy=y2(y+x)44-12y(y+x)4dy

=y2(y+x)24-y10(y+x)5+110(y+x)5dy

=y2(y+x)24-y(y+x)510+(y+x)260

-x0(-xy2(y+x)3dx=(-x)2()44-(-x)510+660

IAB=λ0(-x)24-110(-x)2+1603

=λ0(-x)24-110(-x)+1602

dlABdx=0-(-x)2+10=0

5x=4x=4l5

Subject:PhysicsTopic:RotationSubtopic:Calculation of M.I.
2mℹ️ Source: PYQ_2020

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