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Question-203726




Question Number 203726 by mr W last updated on 27/Jan/24
Commented by mr W last updated on 26/Jan/24
solution to Q#203636
You can't use 'macro parameter character #' in math mode
Answered by mr W last updated on 27/Jan/24
Commented by mr W last updated on 26/Jan/24
Commented by mr W last updated on 27/Jan/24
Commented by mr W last updated on 26/Jan/24
Commented by mr W last updated on 27/Jan/24
Commented by mr W last updated on 27/Jan/24
the center of mass of the three   charges is G, which in current case  must be the centroid of ΔABC,  since they have the same mass.  G must lie vertically under the  hanging point S on the ceiling.  say the sides of ΔABC are p, q, r  respectively.  m_A =AP=((√(2(q^2 +r^2 )−p^2 ))/2)  m_B =BQ=((√(2(r^2 +p^2 )−q^2 ))/2)  m_C =CR=((√(2(p^2 +q^2 )−r^2 ))/2)  d_A =(2/3)m_A =distance from G to A  d_B =(2/3)m_B =distance from G to B  d_C =(2/3)m_C =distance from G to C  say SG=h, SG is vertical.  F_1 =((kQ^2 )/p^2 ) with Q=charge, k=Coulomb constant  F_2 =((kQ^2 )/q^2 )  F_3 =((kQ^2 )/r^2 )  say  F_A  is the resultant from F_2  and F_3   F_B  is the resultant from F_3  and F_1   F_C  is the resultant from F_1  and F_2     T_A , F_A  and mg must be in the same  plane and in equilibrium.  (F_A /d_A )=(T_A /a)=((mg)/h)  ⇒F_A =((mgd_A )/h), T_A =((mga)/h)  similarly  F_B =((mgd_B )/h), T_B =((mgb)/h)  F_C =((mgd_C )/h), T_C =((mgc)/h)    (F_2 /(0.5q))=(F_3 /(0.5r))=(F_A /m_A )=((mgd_A )/(hm_A ))=((2mg)/(3h))  F_2 =((mgq)/(3h))=((kQ^2 )/q^2 ) ⇒q=(((3kQ^2 h)/(mg)))^(1/3)   F_3 =((mgr)/h)=((kQ^2 )/r^2 ) ⇒r=(((3kQ^2 h)/(mg)))^(1/3)   similarly  F_1 =((mgp)/h)=((kQ^2 )/p^2 ) ⇒p=(((3kQ^2 h)/(mg)))^(1/3)   that means p=q=r=(((3kQ^2 h)/(mg)))^(1/3) =((3μ^2 h))^(1/3)   with μ=(√((kQ^2 )/(mg)))    SP=h_P =((√(2(b^2 +c^2 )−p^2 ))/2)  m_A (h^2 +(1/3)m_A ×(2/3)m_A )=(m_A /3)×a^2 +((2m_A )/3)×h_P ^2   h^2 +(2/9)m_A ^2 =(a^2 /3)+((2h_P ^2 )/3)  h^2 +(2/9)×((2(q^2 +r^2 )−p^2 )/4)=(a^2 /3)+((2(b^2 +c^2 )−p^2 )/6)  h^2 +((p^2 +q^2 +r^2 )/9)=((a^2 +b^2 +c^2 )/3)  9h^2 +p^2 +q^2 +r^2 =3(a^2 +b^2 +c^2 )  9h^2 +3((9μ^4 h^2 ))^(1/3) −3(a^2 +b^2 +c^2 )=0  let δ=(√(a^2 +b^2 +c^2 ))  ((h^2 )^(1/3) )^3 +(1/3)((9μ^4 ))^(1/3) ((h^2 )^(1/3) )−(δ^2 /3)=0  ⇒(h^2 )^(1/3) =(((1/3)(√((δ^4 /4)+(μ^4 /9)))+(δ^2 /6)))^(1/3) −(((1/3)(√((δ^4 /4)+(μ^4 /9)))−(δ^2 /6)))^(1/3)   ⇒h=[(((1/3)(√((δ^4 /4)+(μ^4 /9)))+(δ^2 /6)))^(1/3) −(((1/3)(√((δ^4 /4)+(μ^4 /9)))−(δ^2 /6)))^(1/3) ]^(3/2)   (T_A /(mg))=(a/h)=(a/([(((1/3)(√((δ^4 /4)+(μ^4 /9)))+(δ^2 /6)))^(1/3) −(((1/3)(√((δ^4 /4)+(μ^4 /9)))−(δ^2 /6)))^(1/3) ]^(3/2) ))  (T_B /(mg))=(b/h)=(b/([(((1/3)(√((δ^4 /4)+(μ^4 /9)))+(δ^2 /6)))^(1/3) −(((1/3)(√((δ^4 /4)+(μ^4 /9)))−(δ^2 /6)))^(1/3) ]^(3/2) ))  (T_C /(mg))=(c/h)=(c/([(((1/3)(√((δ^4 /4)+(μ^4 /9)))+(δ^2 /6)))^(1/3) −(((1/3)(√((δ^4 /4)+(μ^4 /9)))−(δ^2 /6)))^(1/3) ]^(3/2) ))    special case: a=b=c=s  T_A =T_B =T_C =T  (T/(mg))=(s/([(((√((s^4 /4)+(μ^4 /(81))))+(s^2 /2)))^(1/3) −(((√((s^4 /4)+(μ^4 /(81))))−(s^2 /2)))^(1/3) ]^(3/2) ))
thecenterofmassofthethreechargesisG,whichincurrentcasemustbethecentroidofΔABC,sincetheyhavethesamemass.GmustlieverticallyunderthehangingpointSontheceiling.saythesidesofΔABCarep,q,rrespectively.mA=AP=2(q2+r2)p22mB=BQ=2(r2+p2)q22mC=CR=2(p2+q2)r22dA=23mA=distancefromGtoAdB=23mB=distancefromGtoBdC=23mC=distancefromGtoCsaySG=h,SGisvertical.F1=kQ2p2withQ=charge,k=CoulombconstantF2=kQ2q2F3=kQ2r2sayFAistheresultantfromF2andF3FBistheresultantfromF3andF1FCistheresultantfromF1andF2TA,FAandmgmustbeinthesameplaneandinequilibrium.FAdA=TAa=mghFA=mgdAh,TA=mgahsimilarlyFB=mgdBh,TB=mgbhFC=mgdCh,TC=mgchF20.5q=F30.5r=FAmA=mgdAhmA=2mg3hF2=mgq3h=kQ2q2q=3kQ2hmg3F3=mgrh=kQ2r2r=3kQ2hmg3similarlyF1=mgph=kQ2p2p=3kQ2hmg3thatmeansp=q=r=3kQ2hmg3=3μ2h3withμ=kQ2mgSP=hP=2(b2+c2)p22mA(h2+13mA×23mA)=mA3×a2+2mA3×hP2h2+29mA2=a23+2hP23h2+29×2(q2+r2)p24=a23+2(b2+c2)p26h2+p2+q2+r29=a2+b2+c239h2+p2+q2+r2=3(a2+b2+c2)9h2+39μ4h233(a2+b2+c2)=0letδ=a2+b2+c2(h23)3+139μ43(h23)δ23=0h23=13δ44+μ49+δ26313δ44+μ49δ263h=[13δ44+μ49+δ26313δ44+μ49δ263]32TAmg=ah=a[13δ44+μ49+δ26313δ44+μ49δ263]32TBmg=bh=b[13δ44+μ49+δ26313δ44+μ49δ263]32TCmg=ch=c[13δ44+μ49+δ26313δ44+μ49δ263]32specialcase:a=b=c=sTA=TB=TC=TTmg=s[s44+μ481+s223s44+μ481s223]32
Commented by ajfour last updated on 26/Jan/24
Sir please take a=b=c=s  and  N=3, see if it matches with result  of q.1     Amazing Excellent solution,  m not through yet.
Sirpleasetakea=b=c=sandN=3,seeifitmatcheswithresultofq.1AmazingExcellentsolution,mnotthroughyet.
Commented by mr W last updated on 26/Jan/24
thank you for viewing sir!  i′ll check later.
thankyouforviewingsir!illchecklater.
Commented by mr W last updated on 27/Jan/24
i have fixed a big error.  for the special case with a=b=c=s,  the result is the same as in question 1  with n=3.  it′s interesting to notice that ΔABC  is always equilateral, i.e. p=q=r.
ihavefixedabigerror.forthespecialcasewitha=b=c=s,theresultisthesameasinquestion1withn=3.itsinterestingtonoticethatΔABCisalwaysequilateral,i.e.p=q=r.
Commented by ajfour last updated on 27/Jan/24
At least i understood now that p=q=r, very remarkable!
Answered by mr W last updated on 27/Jan/24
General case:  the particles have different masses  and charges.
Generalcase:theparticleshavedifferentmassesandcharges.
Commented by mr W last updated on 27/Jan/24
Commented by mr W last updated on 27/Jan/24
Commented by mr W last updated on 27/Jan/24
Commented by mr W last updated on 28/Jan/24
Commented by mr W last updated on 28/Jan/24
Commented by mr W last updated on 27/Jan/24
Commented by mr W last updated on 28/Jan/24
say the center of mass of the three   charges is G, which must lie   vertically under the hanging point S  on the ceiling.  say the sides of ΔABC are p, q, r  respectively.  (p_1 /p)=(M_C /(M_B +M_C )) ⇒p_1 =((M_C  p)/(M_B +M_C ))  (p_2 /p)=(M_B /(M_B +M_C )) ⇒p_2 =((M_B  p)/(M_B +M_C ))  m_A =AP  p(m_A ^2 +p_1 p_2 )=p_1 q^2 +p_2 r^2   m_A ^2 +((M_B M_C  p^2 )/((M_B +M_C )^2 ))=((M_C  q^2 +M_B  r^2 )/(M_B +M_C ))  ⇒m_A ^2 =((M_C  q^2 +M_B  r^2 )/(M_B +M_C ))−((M_B M_C  p^2 )/((M_B +M_C )^2 ))  (d_A /m_A )=((M_B +M_C )/(M_A +M_B +M_C ))  (e_A /m_A )=(M_A /(M_A +M_B +M_C ))    say SG=h, SG is vertical.  F_1 =((kQ_B Q_C )/p^2 ) with k=Coulomb constant  F_2 =((kQ_C Q_A )/q^2 )  F_3 =((kQ_A Q_B )/r^2 )  say  F_A  is the resultant from F_2  and F_3   F_B  is the resultant from F_3  and F_1   F_C  is the resultant from F_1  and F_2     T_A , F_A  and M_A g must be in the same  plane and in equilibrium.  (F_A /d_A )=(T_A /a)=((M_A g)/h)  ⇒F_A =((M_A gd_A )/h), T_A =((M_A ga)/h)  similarly  F_B =((M_B gd_B )/h), T_B =((M_B gb)/h)  F_C =((M_C gd_C )/h), T_C =((M_C gc)/h)    (F_2 /((p_1 /p)×q))=(F_3 /((p_2 /p)×r))=(F_A /m_A )=((M_A gd_A )/(hm_A ))=((M_A (M_B +M_C )g)/((M_A +M_B +M_C )h))  ⇒F_2 =((M_C M_A gq)/((M_A +M_B +M_C )h))=((kQ_C Q_A )/q^2 )  ⇒q^3 =((kQ_C Q_A (M_A +M_B +M_C )h)/(gM_C M_A ))  ⇒F_3 =((M_A M_B gr)/((M_A +M_B +M_C )h))=((kQ_A Q_B )/r^2 )  ⇒r^3 =((kQ_A Q_B (M_A +M_B +M_C )h)/(gM_A M_B ))  similarly  ⇒p^3 =((kQ_B Q_C (M_A +M_B +M_C )h)/(gM_B M_C ))  let   μ_1 =(√((kQ_B Q_C (M_A +M_B +M_C ))/(gM_B M_C )))  μ_2 =(√((kQ_C Q_A (M_A +M_B +M_C ))/(gM_C M_A )))  μ_3 =(√((kQ_A Q_B (M_A +M_B +M_C ))/(gM_A M_B )))  ⇒p=((μ_1 ^2 h))^(1/3) , q=((μ_2 ^2 h))^(1/3) , r=((μ_3 ^2 h))^(1/3)     SP=h_P   p(h_P ^2 +p_1 p_2 )=p_1 c^2 +p_2 b^2   h_P ^2 +((M_B M_C p^2 )/((M_B +M_C )^2 ))=((M_C c^2 +M_B b^2 )/(M_B +M_C ))  h_P ^2 =((M_B b^2 +M_C c^2 )/(M_B +M_C ))−((M_B M_C p^2 )/((M_B +M_C )^2 ))    m_A (h^2 +e_A d_A )=e_A a^2 +d_A ×h_P ^2   h^2 +e_A d_A =((M_A a^2 )/(M_A +M_B +M_C ))+(((M_B +M_C )h_P ^2 )/(M_A +M_B +M_C ))  h^2 +((M_A (M_B +M_C )m_A ^2 )/((M_A +M_B +M_C )^2 ))=((M_A a^2 )/(M_A +M_B +M_C ))+(((M_B +M_C )h_P ^2 )/(M_A +M_B +M_C ))  h^2 +((M_A (M_B +M_C ))/((M_A +M_B +M_C )^2 ))×[((M_C  q^2 +M_B  r^2 )/(M_B +M_C ))−((M_B M_C  p^2 )/((M_B +M_C )^2 ))]=((M_A a^2 )/(M_A +M_B +M_C ))+(((M_B +M_C ))/(M_A +M_B +M_C ))×[((M_B b^2 +M_C c^2 )/(M_B +M_C ))−((M_B M_C p^2 )/((M_B +M_C )^2 ))]  h^2 +((M_B M_C p^2 +M_C M_A  q^2 +M_A M_B  r^2 )/((M_A +M_B +M_C )^2 ))=((M_A a^2 +M_B b^2 +M_C c^2 )/(M_A +M_B +M_C ))  h^2 +(((M_B M_C (μ_1 ^4 )^(1/3) +M_C M_A  (μ_2 ^4 )^(1/3) +M_A M_B  (μ_3 ^4 )^(1/3) )(h^2 )^(1/3) )/((M_A +M_B +M_C )^2 ))−((M_A a^2 +M_B b^2 +M_C c^2 )/(M_A +M_B +M_C ))=0  let   ξ=((M_B M_C (μ_1 ^4 )^(1/3) +M_C M_A  (μ_2 ^4 )^(1/3) +M_A M_B  (μ_3 ^4 )^(1/3) )/((M_A +M_B +M_C )^2 ))  or  ξ=((((M_A M_B M_C )/((M_A +M_B +M_C )^4 ))×(((kQ_A Q_B Q_C )/g))^2 ))^(1/3) [(1/( ((M_A Q_A ^2 ))^(1/3) ))+(1/( ((M_B Q_B ^2 ))^(1/3) ))+(1/( ((M_C Q_C ^2 ))^(1/3) ))]  δ=((M_A a^2 +M_B b^2 +M_C c^2 )/(M_A +M_B +M_C ))  ((h^2 )^(1/3) )^3 +ξ((h^2 )^(1/3) )−δ=0  ⇒(h^2 )^(1/3) =(((√((δ^2 /4)+(ξ^3 /(27))))+(δ/2)))^(1/3) −(((√((δ^2 /4)+(ξ^3 /(27))))−(δ/2)))^(1/3)   ⇒h=[(((√((δ^2 /4)+(ξ^3 /(27))))+(δ/2)))^(1/3) −(((√((δ^2 /4)+(ξ^3 /(27))))−(δ/2)))^(1/3) ]^(3/2)   (T_A /(M_A g))=(a/h)  (T_B /(M_B g))=(b/h)  (T_C /(M_C g))=(c/h)
saythecenterofmassofthethreechargesisG,whichmustlieverticallyunderthehangingpointSontheceiling.saythesidesofΔABCarep,q,rrespectively.p1p=MCMB+MCp1=MCpMB+MCp2p=MBMB+MCp2=MBpMB+MCmA=APp(mA2+p1p2)=p1q2+p2r2mA2+MBMCp2(MB+MC)2=MCq2+MBr2MB+MCmA2=MCq2+MBr2MB+MCMBMCp2(MB+MC)2dAmA=MB+MCMA+MB+MCeAmA=MAMA+MB+MCsaySG=h,SGisvertical.F1=kQBQCp2withk=CoulombconstantF2=kQCQAq2F3=kQAQBr2sayFAistheresultantfromF2andF3FBistheresultantfromF3andF1FCistheresultantfromF1andF2TA,FAandMAgmustbeinthesameplaneandinequilibrium.FAdA=TAa=MAghFA=MAgdAh,TA=MAgahsimilarlyFB=MBgdBh,TB=MBgbhFC=MCgdCh,TC=MCgchF2p1p×q=F3p2p×r=FAmA=MAgdAhmA=MA(MB+MC)g(MA+MB+MC)hF2=MCMAgq(MA+MB+MC)h=kQCQAq2q3=kQCQA(MA+MB+MC)hgMCMAF3=MAMBgr(MA+MB+MC)h=kQAQBr2r3=kQAQB(MA+MB+MC)hgMAMBsimilarlyp3=kQBQC(MA+MB+MC)hgMBMCletμ1=kQBQC(MA+MB+MC)gMBMCμ2=kQCQA(MA+MB+MC)gMCMAμ3=kQAQB(MA+MB+MC)gMAMBp=μ12h3,q=μ22h3,r=μ32h3SP=hPp(hP2+p1p2)=p1c2+p2b2hP2+MBMCp2(MB+MC)2=MCc2+MBb2MB+MChP2=MBb2+MCc2MB+MCMBMCp2(MB+MC)2mA(h2+eAdA)=eAa2+dA×hP2h2+eAdA=MAa2MA+MB+MC+(MB+MC)hP2MA+MB+MCh2+MA(MB+MC)mA2(MA+MB+MC)2=MAa2MA+MB+MC+(MB+MC)hP2MA+MB+MCh2+MA(MB+MC)(MA+MB+MC)2×[MCq2+MBr2MB+MCMBMCp2(MB+MC)2]=MAa2MA+MB+MC+(MB+MC)MA+MB+MC×[MBb2+MCc2MB+MCMBMCp2(MB+MC)2]h2+MBMCp2+MCMAq2+MAMBr2(MA+MB+MC)2=MAa2+MBb2+MCc2MA+MB+MCh2+(MBMCμ143+MCMAμ243+MAMBμ343)h23(MA+MB+MC)2MAa2+MBb2+MCc2MA+MB+MC=0letξ=MBMCμ143+MCMAμ243+MAMBμ343(MA+MB+MC)2orξ=MAMBMC(MA+MB+MC)4×(kQAQBQCg)23[1MAQA23+1MBQB23+1MCQC23]δ=MAa2+MBb2+MCc2MA+MB+MC(h23)3+ξ(h23)δ=0h23=δ24+ξ327+δ23δ24+ξ327δ23h=[δ24+ξ327+δ23δ24+ξ327δ23]32TAMAg=ahTBMBg=bhTCMCg=ch
Commented by ajfour last updated on 28/Jan/24
This is beyond praise! Sir. The idea  effort n presentation all. Thanks.
Thisisbeyondpraise!Sir.Theideaeffortnpresentationall.Thanks.

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