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Question Number 27332 by ajfour last updated on 05/Jan/18

Commented by ajfour last updated on 05/Jan/18

Find acceleration of blue and  brown blocks. Friction coefficient  is 𝛍 everywhere (sufficiently less,  and permits motion).

Findaccelerationofblueandbrownblocks.Frictioncoefficientisμeverywhere(sufficientlyless,andpermitsmotion).

Answered by mrW1 last updated on 05/Jan/18

Commented by mrW1 last updated on 05/Jan/18

Commented by mrW1 last updated on 06/Jan/18

(a_2 /a_1 )=tan θ  N_2 =N sin θ−f cos θ=N(sin θ−μ cos θ)  mg−f_2 −N cos θ−f sin θ=ma_2   mg−μN_2 −N (cos θ+μ sin θ)=ma_2   mg−μN(sin θ−μ cos θ)−N (cos θ+μ sin θ)=ma_2   mg−N(2μsin θ−μ^2  cos θ+cos θ)=ma_2     N_1 =mg+N cos θ+f sin θ=mg+N(cos θ+μ sin θ)  N sin θ−f cos θ−f_1 =ma_1   N(sin θ−μ cos θ)−μN_1 =ma_1   N(sin θ−μ cos θ)−μmg−μN(cos θ+μ sin θ)=ma_1   N(sin θ−μ^2  sin θ−2μ cos θ)−μmg=ma_1     ((mg−N(2μsin θ−μ^2  cos θ+cos θ))/(N(sin θ−μ^2  sin θ−2μ cos θ)−μmg))=((ma_2 )/(ma_1 ))=tan θ=((sin θ)/(cos θ))  mg cos θ−N(2μsin θ cos θ−μ^2  cos^2  θ+cos^2  θ)=N(sin^2  θ−μ^2  sin^2  θ−2μ sin θ cos θ)−μmg sin θ  N(2μsin θ cos θ−μ^2  cos^2  θ+cos^2  θ+sin^2  θ−μ^2  sin^2  θ−2μ sin θ cos θ)=mg(cos θ+μsin θ)  N(1−μ^2 )=mg(cos θ+μsin θ)  ⇒N=(((cos θ+μ sin θ)mg)/(1−μ^2 ))    a_1 =((N(sin θ−μ^2  sin θ−2μ cos θ))/m)−μg  a_1 =(((cos θ+μ sin θ)(sin θ−μ^2  sin θ−2μ cos θ)g)/(1−μ^2 ))−μg  ⇒a_1 =[(cos θ+μ sin θ)(sin θ−((2μ)/(1−μ^2 )) cos θ)−μ]g    a_2 =g−((N(2μ sin θ+cos θ−μ^2  cos θ))/m)  a_2 =g−(((cos θ+μ sin θ)(2μ sin θ+cos θ−μ^2  cos θ)g)/(1−μ^2 ))  ⇒a_2 =[1−(cos θ+μ sin θ)(((2μ)/(1−μ^2 )) sin θ+cos θ)]g

a2a1=tanθN2=Nsinθfcosθ=N(sinθμcosθ)mgf2Ncosθfsinθ=ma2mgμN2N(cosθ+μsinθ)=ma2mgμN(sinθμcosθ)N(cosθ+μsinθ)=ma2mgN(2μsinθμ2cosθ+cosθ)=ma2N1=mg+Ncosθ+fsinθ=mg+N(cosθ+μsinθ)Nsinθfcosθf1=ma1N(sinθμcosθ)μN1=ma1N(sinθμcosθ)μmgμN(cosθ+μsinθ)=ma1N(sinθμ2sinθ2μcosθ)μmg=ma1mgN(2μsinθμ2cosθ+cosθ)N(sinθμ2sinθ2μcosθ)μmg=ma2ma1=tanθ=sinθcosθmgcosθN(2μsinθcosθμ2cos2θ+cos2θ)=N(sin2θμ2sin2θ2μsinθcosθ)μmgsinθN(2μsinθcosθμ2cos2θ+cos2θ+sin2θμ2sin2θ2μsinθcosθ)=mg(cosθ+μsinθ)N(1μ2)=mg(cosθ+μsinθ)N=(cosθ+μsinθ)mg1μ2a1=N(sinθμ2sinθ2μcosθ)mμga1=(cosθ+μsinθ)(sinθμ2sinθ2μcosθ)g1μ2μga1=[(cosθ+μsinθ)(sinθ2μ1μ2cosθ)μ]ga2=gN(2μsinθ+cosθμ2cosθ)ma2=g(cosθ+μsinθ)(2μsinθ+cosθμ2cosθ)g1μ2a2=[1(cosθ+μsinθ)(2μ1μ2sinθ+cosθ)]g

Commented by ajfour last updated on 05/Jan/18

Excellently presented and  handled Sir!

ExcellentlypresentedandhandledSir!

Commented by mrW1 last updated on 06/Jan/18

Thank you sir!  I have a problem with the result, to  be exact, with the term (1/(1−μ^2 )). It  means μ≠1. But why is it so? What  happens if μ=1?

Thankyousir!Ihaveaproblemwiththeresult,tobeexact,withtheterm11μ2.Itmeansμ1.Butwhyisitso?Whathappensifμ=1?

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