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Question Number 129795 by ajfour last updated on 19/Jan/21

Commented by ajfour last updated on 19/Jan/21

Q.129660   (Revisit)

Q.129660(Revisit)

Answered by ajfour last updated on 23/Jan/21

Commented by ajfour last updated on 23/Jan/21

From work-energy balance  mg((L/2))[sin 2φ_0 −sin 2φ]  =(1/2)m(v_(cm) ^2 )+(1/2)I_(cm) ω^2   ucos 2φ−v=−Rcosec^2 φ((dφ/dt))  OP =p=Rcot φ  (dp/dt)=−(Rcosec^2 φ)(dφ/dt)=u  ⇒  (dφ/dt)=−(u/R)sin^2 φ  usin 2φ=ωRcot φ  v_(cm) ^2 =v_(x,cm) ^2 +v_(y,cm) ^2    v_x =(d/dt)(Rcot φ−(L/2)cos 2φ)   v_y =(d/dt)((L/2)sin 2φ)  v_(cm) ^2 =(Lsin 2φ−Rcosec^2 φ)^2 ((dφ/dt))^2     +(Lcos 2φ)^2 ((dφ/dt))^2   ω=((usin 2φ)/(Rcot φ))=−(((cosec^2 φsin 2φ)/(cot φ)))(dφ/dt)  −−−−−−−−−−−−−−−  gL(sin 2φ_0 −sin 2φ)  =((dφ/dt))^2 [(I_(cm) /m)(((cosec^2 φsin 2φ)/(cot φ)))^2      +(Lsin 2φ−Rcosec^2 φ)^2     +(Lcos 2φ)^2 ]  ⇒  ((dφ/dt))^2 =((gL(sin 2φ_0 −sin 2φ))/((I_(cm) /m)(((cosec^2 φsin 2φ)/(cot φ)))^2 +(Lsin 2φ−Rcosec^2 φ)^2 +(Lcos 2φ)^2 ))  ω^2 =((4gL(sin 2φ_0 −sin 2φ_1 ))/(((4L^2 )/3)+R^2 cosec^4 φ−4RLcot φ))  ω^2 =((12gλ(sin α−sin θ))/(R(4λ^2 +3cosec^4 (θ/2)−12λcot (θ/2))))  say   φ=φ_1 =tan^(−1) ((R/L))  Now phase II starts:  ...............................

Fromworkenergybalancemg(L2)[sin2ϕ0sin2ϕ]=12m(vcm2)+12Icmω2ucos2ϕv=Rcosec2ϕ(dϕdt)OP=p=Rcotϕdpdt=(Rcosec2ϕ)dϕdt=udϕdt=uRsin2ϕusin2ϕ=ωRcotϕvcm2=vx,cm2+vy,cm2vx=ddt(RcotϕL2cos2ϕ)vy=ddt(L2sin2ϕ)vcm2=(Lsin2ϕRcosec2ϕ)2(dϕdt)2+(Lcos2ϕ)2(dϕdt)2ω=usin2ϕRcotϕ=(cosec2ϕsin2ϕcotϕ)dϕdtgL(sin2ϕ0sin2ϕ)=(dϕdt)2[Icmm(cosec2ϕsin2ϕcotϕ)2+(Lsin2ϕRcosec2ϕ)2+(Lcos2ϕ)2](dϕdt)2=gL(sin2ϕ0sin2ϕ)Icmm(cosec2ϕsin2ϕcotϕ)2+(Lsin2ϕRcosec2ϕ)2+(Lcos2ϕ)2ω2=4gL(sin2ϕ0sin2ϕ1)4L23+R2cosec4ϕ4RLcotϕω2=12gλ(sinαsinθ)R(4λ2+3cosec4θ212λcotθ2)sayϕ=ϕ1=tan1(RL)NowphaseIIstarts:...............................

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