Re: newbie here,, need help with parametrics

*To*: mathgroup at smc.vnet.net*Subject*: [mg96509] Re: newbie here,, need help with parametrics*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Sun, 15 Feb 2009 03:20:39 -0500 (EST)*References*: <gn5u3e$gko$1@smc.vnet.net>

Hi, we love to make high school home-works ! With[{g = 9.81, x = 0, y = 0}, Manipulate[ Block[{tEnd}, tEnd = 2*v*Sin[\[Alpha]]/g; ParametricPlot[ {x + v Cos [\[Alpha]]*t, y + v Sin [\[Alpha]]*t - g*t^2/2}, {t, 0, tEnd}]], {{v, 20, "Speed"}, 0, 50}, {{\[Alpha], Pi/4, "Angle"}, 0, Pi/2}] ] Regards Jens R.J. wrote: > I am using Mathematica and i'd rather be using derive,,,,, but anyways,, heres the problem i have to do, a baseball is thrown from the stands 32 feet from the ground at an angle of 30 degrees above the horizontal, initial velocity is 32 feet per second. > > what i want to do is find how to plot this in mathematica,, the graph i keep getting says it hits the ground after .8 seconds, and i know thats not right,,, here is the formula i am using > > r = (x + v Cos a) t) i + (y + (v Sin a) t - 1/2 gt^2) j > > where x is the initial x position and y is the initial height, v is the initial velocity a is the angle (30*) t is time and g is the gravitational constant.. > > i'm stuck,,, any help? >