Re: A problem with Manipulate

*To*: mathgroup at smc.vnet.net*Subject*: [mg127903] Re: A problem with Manipulate*From*: Dominik Hezel <sendme2000 at me.com>*Date*: Fri, 31 Aug 2012 03:57:45 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <k1ch1e$n2t$1@smc.vnet.net>

On Sunday, August 26, 2012 8:51:26 AM UTC+2, Sergio Miguel Terrazas Porras wrote: > Hello guys, I am having a problem with a Manipulate I wrote, to ilustrate a physics problem. > > > > If you aim at an object that is hanging a height H at a distance D. And at the instant you shoot, the object starts to fall, you will alwais hit it, regardless os the initial speed (provided the floor does not interfere). > > > > > > > > However, if I make an evaluation, it works fine, but when I change the speed, it "remembers" the time of flight of the preceding speed. > > > > > > > > I will appreciate any help, as I am frustrated at not beeig able to fix the problem. > > > > > > > > Thanks > > > > > > > > > > > > d;H=10;r01={0,0};\[Theta]=ArcTan[H/d];a=9.8*{0,-1}; > > r02={d,H}; > > chango > > chango:=Manipulate[Module[{v0,r1,r2,linea,flecha,chango}, > > v0=vi*{Cos[\[Theta]],Sin[\[Theta]]}; > > r1[t_]=r01+v0*t+1/2 a*t^2; > > r2[t_]=r02+1/2 a*t^2; > > > > linea=Graphics[{Red,Dashing[{.01,.01}],Line[{r01,r02}]}]; > > > > flecha=Graphics[Arrow[{r01,r2[t]}]]; > > > > trayectoria1=ParametricPlot[r1[z],{z,0,t+.001}]; > > > > trayectoria2=ParametricPlot[r2[z],{z,0,t+.001},PlotStyle->{Dashing[.02],Brown}]; > > > > chango=Graphics[{Brown,PointSize[.03],Point[r2[t]]}]; > > > > > > > > > > > > (*Time of Flight*) > > tf=Dynamic[H/(vi*Sin[\[Theta]])]; > > > > > > > > > > > > Show[flecha,chango,linea,trayectoria1,trayectoria2,PlotRange->All] > > ] > > ,{{vi,10,"Subscript[v, i]"},{10,15,20}},{{t,0},0,tf,Appearance->"Labeled"},TrackedSymbols->{vi,t,tf},SaveDefinitions->True] Some of the code is opaque to me, but if you define 'd' at the very beginning, at least something happens and it's not all red.