{VERSION 5 0 "APPLE_PPC_MAC" "5.0" } {USTYLETAB {CSTYLE "Maple Input" -1 0 "Courier" 0 1 255 0 0 1 0 1 0 0 1 0 0 0 0 1 }{CSTYLE "2D Math" -1 2 "Times" 0 1 0 0 0 0 0 0 2 0 0 0 0 0 0 1 }{CSTYLE "2D Comment" 2 18 "" 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 256 "" 1 24 0 0 0 0 0 1 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 257 "" 1 10 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 258 "" 1 18 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 259 "" 1 18 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{PSTYLE "Normal" -1 0 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }1 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "Headi ng 1" -1 3 1 {CSTYLE "" -1 -1 "Times" 1 18 0 0 0 1 2 1 2 2 2 2 1 1 1 1 }1 1 0 0 6 6 1 0 1 0 2 2 0 1 }{PSTYLE "Heading 2" -1 4 1 {CSTYLE "" -1 -1 "Times" 1 14 0 0 0 1 2 1 2 2 2 2 1 1 1 1 }1 1 0 0 8 2 1 0 1 0 2 2 0 1 }{PSTYLE "PageBreak" -1 256 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }1 1 0 0 0 0 1 0 1 0 1 2 0 1 }{PSTYLE "Normal " -1 257 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 } 3 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "Normal" -1 258 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }3 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "Normal" -1 259 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }3 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "Normal" -1 260 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }3 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "Normal" -1 261 1 {CSTYLE "" -1 -1 "T imes" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }3 1 0 0 0 0 1 0 1 0 2 2 0 1 } {PSTYLE "Maple Output" -1 262 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }1 3 0 0 0 0 1 0 1 0 2 2 0 1 }} {SECT 0 {EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 258 "" 0 "" {TEXT -1 0 "" }}{PARA 257 "" 0 "" {TEXT 256 12 "2D ROTATIONS" }} {PARA 260 "" 0 "" {TEXT 259 11 "Tevian Dray" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 259 "" 0 "" {TEXT 257 33 "copyright 1998 & 2000 Tevian Dray" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 261 "" 0 "" {TEXT 258 72 "In this worksheet, you will look at the world from a rotating turn table." }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}}{SECT 1 {PARA 3 "" 0 "" {TEXT -1 14 "Initialization" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 49 "restart:with(plots):with(plottools):with(linalg):" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1264 "# 2Ddefs\n\n# Release 4:\n#Machin e:=substring(interface(version),39..41):\n# Release 5.1:\n#Machine:=su bstring(interface(version),41..43):\n# Fixed?\nMachine:=IBM:\n\nArrow: =proc(base,dir,color)\n local Dir:\n global Machine:\n if Machine=` IBM` or Machine=`DEC` or Machine=`SUN` then\n Dir:=base+dir\n else \n Dir:=dir\n fi;\n arrow(base,Dir,0.02,0.05,0.1,color)\nend:\n\n wb:=.02:\nwh:=.05:\nhh:=.1:\n\nd:=disk([0,0],1,color=wheat):\n\nQ:=[co s(Pi/6),sin(Pi/6)]*2/5:\nP:=[cos(Pi/6)*2/5,4/5]:\nOO:=[0,0]:\n\nMyText Plot:=proc(pt,label,alignment)\n textplot([pt[1],pt[2],label],alignme nt,font=[TIMES,BOLD,12])\nend:\n\nVvec:=\{Arrow(OO,P-OO,color=blue),\n \011Arrow(OO,Q-OO,color=green),\n\011Arrow(Q,P-Q,color=green)\}:\nVlbl :=\{MyTextPlot(Q/3,` R*r[hat] `,align=\{BELOW,RIGHT\}),\n\011\011MyTex tPlot((P+Q)/2,` r[rel] `,align=RIGHT),\n\011\011MyTextPlot(P/2,` r[fix ] `,align=\{ABOVE,LEFT\}),\n\011\011MyTextPlot(OO,` O `,align=\{BELOW, LEFT\}),\n\011\011MyTextPlot(P,`(x,y)`,align=ABOVE),\n\011\011MyTextPl ot(Q,` Q `,align=\{BELOW,RIGHT\})\}:\n\nQx:=Q[1]:\nQy:=Q[2]:\nQcos:=0. 25*cos(Pi/6):\nQsin:=0.25*sin(Pi/6):\nRTvec:=\{Arrow(Q,[Qcos,Qsin],col or=red),\n\011Arrow(Q,[-Qsin,Qcos],color=red)\}:\nRTlbl:=\n \{textplo t([Qx+Qcos,Qy+Qsin,` R `],align=\{BELOW,RIGHT\},font=[TIMES,ROMAN,12]) ,\n textplot([Qx-Qsin,Qy+Qcos,` Q `],align=\{BELOW,RIGHT\},font=[SYM BOL,12])\}:\n" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}}{SECT 1 {PARA 3 "" 0 "" {TEXT -1 8 "Notation" }} {PARA 0 "" 0 "" {TEXT -1 26 "Consider a fixed observer " }{XPPEDIT 18 0 "Q" "6#%\"QG" }{TEXT -1 20 " located a distance " }{XPPEDIT 18 0 "R " "6#%\"RG" }{TEXT -1 55 " from the origin, so that in polar coordinat es we have " }{XPPEDIT 18 0 "Q=[R,theta]" "6#/%\"QG7$%\"RG%&thetaG" } {TEXT -1 42 ". The natural orthonormal polar basis at " }{XPPEDIT 18 0 "Q" "6#%\"QG" }{TEXT -1 4 " is:" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 70 "r[hat]:=[cos(Theta),sin(Theta)];\ntheta[hat]:=[-sin(T heta),cos(Theta)];" }}}{PARA 262 "" 1 "" {TEXT -1 48 "With respect to \+ this basis, the position vector " }{XPPEDIT 18 0 "r" "6#%\"rG" }{TEXT -1 19 " can be written as:" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 26 "r[fix]:=R*'r[hat]'+r[rel];" }}}{PARA 0 "" 0 "" {TEXT -1 33 "as sho wn in the following figure:" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 18 "plotsetup(inline):" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 37 "d isplay(Vvec,Vlbl,RTvec,d,axes=NONE);" }}}{PARA 0 "" 0 "" {TEXT -1 66 " In order to consider a rotating observer, all we have to do is set" }} {EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 15 "Theta:=Omega*t;" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 0 "" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" } }}{SECT 1 {PARA 3 "" 0 "" {TEXT -1 25 "Velocity and Acceleration" }} {PARA 0 "" 0 "" {TEXT -1 50 "Now consider a moving object with positio n vector " }{XPPEDIT 18 0 "r(t)" "6#-%\"rG6#%\"tG" }{TEXT -1 72 ". In the nonrotating frame, the velocity and acceleration are given by " } {XPPEDIT 18 0 "v[fix](t)=diff(r[fix](t),t)" "6#/-&%\"vG6#%$fixG6#%\"tG -%%diffG6$-&%\"rG6#F(6#F*F*" }{TEXT -1 5 " and " }{XPPEDIT 18 0 "a[fix ](t)=diff(v[fix](t),t)" "6#/-&%\"aG6#%$fixG6#%\"tG-%%diffG6$-&%\"vG6#F (6#F*F*" }{TEXT -1 139 ", respectively. In the rotating frame, things are not quite so simple, since the rotating observer is not aware of \+ the rotation. Thus, if" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 40 "r [rel]:=X(t)*'r[hat]'+Y(t)*'theta[hat]';" }}}{PARA 0 "" 0 "" {TEXT -1 92 "then the rotating observer computes the velocity and acceleration \+ simply by differentiating " }{XPPEDIT 18 0 "f(t)" "6#-%\"fG6#%\"tG" } {TEXT -1 5 " and " }{XPPEDIT 18 0 "g(t)" "6#-%\"gG6#%\"tG" }{TEXT -1 37 ". The rotating observer thus obtains" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 59 "v[rel]:=\n diff(X(t),t)*'r[hat]'+diff(Y(t),t)*'theta [hat]';" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 63 "a[rel]:=\n diff (X(t),t,t)*'r[hat]'+diff(Y(t),t,t)*'theta[hat]';" }}}{PARA 0 "" 0 "" {TEXT -1 68 "These differ from the true velocity and acceleration for \+ 2 reasons: " }{XPPEDIT 18 0 "r[rel]" "6#&%\"rG6#%$relG" }{TEXT -1 20 " is not the same as " }{XPPEDIT 18 0 "r[fix]" "6#&%\"rG6#%$fixG" } {TEXT -1 47 ", and the time dependence of the basis vectors " } {XPPEDIT 18 0 "R" "6#%\"RG" }{TEXT -1 5 " and " }{XPPEDIT 18 0 "Theta " "6#%&ThetaG" }{TEXT -1 27 " has been ignored. We have" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 31 "v[Fix]:=expand(diff(r[fix],t)):" }} }{PARA 0 "" 0 "" {TEXT -1 54 "which we expand with respect to the orth onormal basis " }{XPPEDIT 18 0 "\{R,Theta\}" "6#<$%\"RG%&ThetaG" } {TEXT -1 1 ":" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 128 "v[fix]:=\n simplify(dotprod(v[Fix],r[hat],orthogonal))*'r[hat]'+\n simplify(do tprod(v[Fix],theta[hat],orthogonal))*'theta[hat]';" }}}{PARA 0 "" 0 " " {TEXT -1 44 "Similarly, computing the acceleration yields" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 152 "a[Fix]:=diff(v[Fix],t):\na[fix]:= \n simplify(dotprod(a[Fix],r[hat],orthogonal))*'r[hat]'+\n simplify( dotprod(a[Fix],theta[hat],orthogonal))*'theta[hat]';" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 0 "" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}} {SECT 1 {PARA 3 "" 0 "" {TEXT -1 13 "Linear Motion" }}{PARA 0 "" 0 "" {TEXT -1 93 "Consider now the case of linear motion, for which the tru e acceleration must vanish, so that " }{XPPEDIT 18 0 "a[fix]=0" "6#/&% \"aG6#%$fixG\"\"!" }{TEXT -1 60 ". The previous equation yields a dif ferential equation for " }{XPPEDIT 18 0 "X(t)" "6#-%\"XG6#%\"tG" } {TEXT -1 5 " and " }{XPPEDIT 18 0 "Y(t)" "6#-%\"YG6#%\"tG" }{TEXT -1 17 " which determine " }{XPPEDIT 18 0 "r[rel" "6#&%\"rG6#%$relG" } {TEXT -1 57 ". There are 2 ways to solve this differential equtation. " }}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 11 "Using Maple" }}{PARA 0 "" 0 " " {TEXT -1 103 "Maple has a command \"dsolve\" which can solve many di fferential equations. For further information, try" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 7 "?dsolve" }}}{PARA 0 "" 0 "" {TEXT -1 23 "Her e our equations are " }{XPPEDIT 18 0 "a[fix]" "6#&%\"aG6#%$fixG" } {TEXT -1 39 " and our \"variables\" are the functions " }{XPPEDIT 18 0 "X(t)" "6#-%\"XG6#%\"tG" }{TEXT -1 5 " and " }{XPPEDIT 18 0 "Y(t)" " 6#-%\"YG6#%\"tG" }{TEXT -1 1 "." }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 118 "eq1:=simplify(dotprod(a[Fix],r[hat])):\neq2:=simplify(dotprod (a[Fix],theta[hat])):\nsols:=dsolve(\{eq1,eq2\},\{X(t),Y(t)\});" }}} {EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 0 "" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 42 "Converting the Equatio n of a Straight Line" }}{PARA 0 "" 0 "" {TEXT -1 186 "A more intuitive way to solve this differential equation is to realize that the soluti ons must be straight lines, but expressed in the rotating frame. The \+ equation of a straight line is" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 26 "r[fix]:='r[0]'+t*'v[fix]';" }}}{PARA 0 "" 0 "" {TEXT -1 5 "where " }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 39 "r[0]:=[x[0],y[0]];\nv[fi x]:=[v[x],v[y]];" }}}{PARA 0 "" 0 "" {TEXT -1 30 "In the rotating fram e, we have" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 37 "r[REL]:='r[0]' +t*'v[fix]'-R*'r[hat]';" }}}{PARA 0 "" 0 "" {TEXT -1 17 "or in other w ords" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 128 "r[Rel]:=\n simplif y(dotprod(r[REL],r[hat],orthogonal))*'r[hat]'+\n simplify(dotprod(r[R EL],theta[hat],orthogonal))*'theta[hat]';" }}}{EXCHG {PARA 0 "> " 0 " " {MPLTEXT 1 0 0 "" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 10 "Comparison" }}{PARA 0 "" 0 "" {TEXT -1 59 "The \+ constants in these 2 approaches are related as follows:" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 40 "d1:=expand(subs(t=0,subs(sols,r[rel ])));" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 29 "d2:=expand(subs(t= 0,r[Rel]));" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 54 "const1:=solv e(\n \{d1[1]=d2[1],d1[2]=d2[2]\},\{_C1,_C2\});" }}}{EXCHG {PARA 0 "> \+ " 0 "" {MPLTEXT 1 0 65 "d3:=expand(subs(const1,\n subs(t=Pi/2/Omega,s ubs(sols,r[rel]))));" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 38 "d4: =expand(subs(t=Pi/2/Omega,r[Rel]));" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 54 "const2:=solve(\n \{d3[1]=d4[1],d3[2]=d4[2]\},\{_C3,_ C4\});" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 0 "" }}}}}}{MARK "5" 0 }{VIEWOPTS 1 1 0 3 2 1804 1 1 1 1 }{PAGENUMBERS 0 1 2 33 1 1 }