Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2000
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2000

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Parametric Solving Question From 14 Year Old

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23534] Re: [mg23507] Parametric Solving Question From 14 Year Old
  • From: BobHanlon at aol.com
  • Date: Tue, 16 May 2000 22:30:05 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 5/16/2000 3:06:22 AM, alana at mac.com writes:

>    I am 14 and am wondering how to solve parametric equations directly
>without graphing in Mathematica? I am figuring out when a projectile in
>motion hits the ground only due to the even force of gravity acting upon
>it. The parametric equation is:
>
>x(t)=15*t*Cos[60]
>y(t)=15*t*Sin[60]-9.80665/2*t^2
>
>I want to find the value x(t) and t when y(t)=0.
>

x[t_] := Evaluate[15*t*Cos[60 Degree]];

y[t_] := Evaluate[15*t*Sin[60 Degree] - 9.80665/2*t^2];

Note that arguments to trig functions must be given in radians. Angles given 
in degrees need to be multiplied by Degree to convert the argument to radians.

tmax = Max[t /. Solve[y[t] == 0, t]]

2.6493

xmax = x[tmax]

19.8698

Plot[{x[t], y[t]}, {t, 0, tmax}, 
    PlotStyle -> {RGBColor[0, 0, 1], RGBColor[1, 0, 0]}, PlotRange -> All, 
    AxesLabel -> {"t", {StyleForm["x[t]", FontColor -> RGBColor[0, 0, 1]], 
          StyleForm["y[t]", FontColor -> RGBColor[1, 0, 0]]}}];

y[t /. Solve[x == x[t], t]]

{Sqrt[3]*x - 0.0871702*x^2}

Plot[%, {x, 0, xmax}, PlotStyle -> RGBColor[1, 0, 0], 
    AxesLabel -> {"x", StyleForm["y[x]", FontColor -> RGBColor[1, 0, 0]]}];


Bob

BobHanlon at aol.com


  • Prev by Date: Re: Parametric Solving Question From 14 Year Old
  • Next by Date: AW: Sorting with Infinity
  • Previous by thread: Re: Parametric Solving Question From 14 Year Old
  • Next by thread: RE: Parametric Solving Question From 14 Year Old