www.pudn.com > matlab±à³Ì.zip > ball.m, change:1998-01-01,size:3132b

%  Script file: ball.m 
% 
%  Purpose:  
%    This program calculates the distance traveled by a ball  
%    thrown at a specified angle "theta" and a specified 
%    velocity "vo" from a point on the surface of the Earth, 
%    ignoring air friction and the Earth's curvature.  It  
%    calculates the angle yielding maximum range, and also 
%    plots selected trajectories. 
% 
%  Record of revisions: 
%      Date       Programmer          Description of change 
%      ====       ==========          ===================== 
%    12/10/97    S. J. Chapman        Original code  
% 
% Define variables: 
%   conv         -- Degrees to radians conv factor 
%   gravity      -- Accel. due to gravity (m/s^2) 
%   ii, jj       -- Loop index 
%   index        -- Location of maximum range in array 
%   maxangle     -- Angle that gives maximum range (deg) 
%   maxrange     -- Maximum range (m) 
%   range        -- Range for a particular angle (m) 
%   time         -- Time (s) 
%   theta        -- Initial angle (deg) 
%   traj_time    -- Total trajectory time (s) 
%   vo           -- Initial velocity (m/s) 
%   vxo          -- X-component of initial velocity (m/s) 
%   vyo          -- Y-component of initial velocity (m/s) 
%   x            -- X-position of ball (m) 
%   y            -- Y-position of ball (m) 
 
%  Constants 
conv = pi / 180;      % Degrees-to-radians conversion factor 
g = -9.81;            % Accel. due to gravity 
vo = 20;              % Initial velocity 
 
%Create an array to hold ranges 
range = zeros(1,91); 
 
% Calculate maximum ranges 
for ii = 1:91 
   theta = ii - 1; 
   vxo = vo * cos(theta*conv); 
   vyo = vo * sin(theta*conv); 
   traj_time = -2 * vyo / g; 
   range(ii) = vxo * traj_time; 
end 
 
% Write out table of ranges 
fprintf ('Range versus angle theta:\n'); 
for ii = 1:91 
   theta = ii - 1; 
   fprintf('  %2d    %8.4f\n',theta, range(ii)); 
end 
 
% Calculate the maximum range and angle 
[maxrange index] = max(range); 
maxangle = index - 1; 
fprintf ('\nMax range is %8.4f at %2d degrees.\n',... 
         maxrange, maxangle); 
 
% Now plot the trajectories 
for ii = 5:10:85 
 
   % Get velocities and max time for this angle 
   theta = ii; 
   vxo = vo * cos(theta*conv); 
   vyo = vo * sin(theta*conv); 
   traj_time = -2 * vyo / g; 
 
   % Calculate the (x,y) positions 
   x = zeros(1,21); 
   y = zeros(1,21); 
   for jj = 1:21 
      time = (jj-1) * traj_time/20; 
      x(jj) = vxo * time; 
      y(jj) = vyo * time + 0.5 * g * time^2; 
   end 
   plot(x,y,'b'); 
   if ii == 5 
      hold on;  
   end 
end 
 
% Add titles and axis lables 
title ('\bfTrajectory of Ball vs Initial Angle \theta'); 
xlabel ('\bf\itx \rm\bf(meters)'); 
ylabel ('\bf\ity \rm\bf(meters)'); 
axis ([0 45 0 25]); 
grid on; 
 
% Now plot the max range trajectory 
vxo = vo * cos(maxangle*conv); 
vyo = vo * sin(maxangle*conv); 
traj_time = -2 * vyo / g; 
 
% Calculate the (x,y) positions 
x = zeros(1,21); 
y = zeros(1,21); 
for jj = 1:21 
   time = (jj-1) * traj_time/20; 
   x(jj) = vxo * time; 
   y(jj) = vyo * time + 0.5 * g * time^2; 
end 
plot(x,y,'r','LineWidth',3.0); 
hold off