Checked content

File:Parabolic trajectory.svg

Description Illustration of a parabolic trajectory.
Date 05:58, 20 December 2007 (UTC)
Source self-made with MATLAB. Tweaked in Inkscape.
Author Oleg Alexandrov
Public domain I, the copyright holder of this work, release this work into the public domain. This applies worldwide.
In some countries this may not be legally possible; if so:
I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

Source code ( MATLAB)

% illustration of a parabolic trajectory
function main()
   arrow_size = 0.1;
   sharpness = 20;
   arrow_type = 1; 
   arrlen = 0.3; % arrow length
   tiny = 0.01;
   ball_radius = 0.05;
   X=linspace(-L, L, N);
   Y =L^2 - X.^2;
   Xl = linspace(-L-s, L+s, N);
% KSmrq's colors
   red    = [0.867 0.06 0.14];
   blue   = [0, 129, 205]/256;
   green  = [0, 200,  70]/256;
   yellow = [254, 194,   0]/256;
   white = 0.99*[1, 1, 1];
   black = [0, 0, 0];
   gray = 0.5*white;
   lw = 2.3;
   figure(1); clf; hold on; axis equal; axis off;
   plot(X, Y, 'linewidth', lw, 'linestyle', '--', 'colour', blue);
   arrow([q-tiny, L^2-q^2], [q+arrlen-tiny, L^2-q^2-2*q*arrlen], lw, arrow_size, sharpness, arrow_type, red);
   ball(q, L^2 - q^2, ball_radius, gray)
   plot(Xl, 0*Xl, 'linewidth', 2*lw, 'colour', black);
  %saveas(gcf, 'Parabolic_trajectory.eps', 'psc2')
function ball(x, y, radius, colour) % draw a ball of given uniform colour 
   H=fill(X, Y, colour);
   set(H, 'EdgeColor', [0, 0, 0]);
function arrow(start, stop, thickness, arrow_size, sharpness, arrow_type, colour)
% Function arguments:
% start, stop:  start and end coordinates of arrow, vectors of size 2
% thickness:    thickness of arrow stick
% arrow_size:   the size of the two sides of the angle in this picture ->
% sharpness:    angle between the arrow stick and arrow side, in degrees
% arrow_type:   1 for filled arrow, otherwise the arrow will be just two segments
% color:        arrow colour, a vector of length three with values in [0, 1]
% convert to complex numbers
   start=start(1)+i*start(2); stop=stop(1)+i*stop(2);
% points making up the arrow tip (besides the "stop" point)
   point1 = stop - (arrow_size*rotate_angle)*(stop-start)/abs(stop-start);
   point2 = stop - (arrow_size/rotate_angle)*(stop-start)/abs(stop-start);
   if arrow_type==1 % filled arrow
      % plot the stick, but not till the end, looks bad
      t=0.5*arrow_size*cos(pi*sharpness/180)/abs(stop-start); stop1=t*start+(1-t)*stop;
      plot(real([start, stop1]), imag([start, stop1]), 'LineWidth', thickness, 'Colour', colour);
      % fill the arrow
      H=fill(real([stop, point1, point2]), imag([stop, point1, point2]), colour);
      set(H, 'EdgeColor', 'none')
   else % two-segment arrow
      plot(real([start, stop]), imag([start, stop]),   'LineWidth', thickness, 'Colour', colour); 
      plot(real([stop, point1]), imag([stop, point1]), 'LineWidth', thickness, 'Colour', colour);
      plot(real([stop, point2]), imag([stop, point2]), 'LineWidth', thickness, 'Colour', colour);
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