Projectile motion Graph error

Question

Ziad Al Malouf 2020-4-27

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/520991-projectile-motion-graph-error

评论： Ameer Hamza 2020-4-27

My Graph continues to the right... where i need it to stop at y=0 ( upon landing).. can someone help me resolve this issue.

clc
clear all
close all
format long
V = input('Enter velocity: ') % user enters initial Velocity in m/s
g= input('Enter acceleration due to gravity: ') % user enters gravity acceleration in m/s^2
theta= input('Enter angle: ') % user enters angle in degrees
y0=input('Enter Initial height: ') %user Enters the initial Height in m
Fs = input('Enter constant force spring force= '); %Constant force spring force, Fs (N)
t=0:0.1:5; %Time Vector; When this is changed, the value of x changes.
% please change only to shorten the simulation time.
figure
set(gcf,'position',[50,50,1200,500])
%close all
Vx = V.*cosd(theta) % Component of X value
Vy = V.*sind(theta)
% loop that goes through to get the x and y values and plots them using the
% built in plot function and stops while time(t) is reached
for i= 1:length(t)
%Vy = V.*cosd(theta)-g*t(i)
x=Vx*t(i); %Formula to find X
y=y0+V.*sind(theta)*t(i)-g*t(i)^2; % Formula to find Y
  
% Find all the indices of y that are less than zero
zeroIdx = find(y < 0);
% If there are indices with altitude less than zero, find the first one and set the X axis limits
if ~isempty(zeroIdx)
finalPosition = y(zeroIdx(1));
if(finalPosition>0)
xlim([0, finalPosition])
else
xlim([finalPosition,0])
end
end
% Set all altitudes less than zero to zero (can't penetrate the ground!)
y(zeroIdx) = 0;
  
plot(x,y,'o','MarkerFacecolor','b')
hold all
axis equal
xlabel('x in meters')
ylabel('y in meters')
xlim([0 180]) % the second value in the brackets sets the limit for the X axis
ylim([0 100]) % the second value in the brackets sets the limit for the Y axis
  
grid on
drawnow
end
k=Fs./x;
fprintf("%i",k)
zoom on;
maxh= max(y) % find the max height by finding Y max using the max() function
maxpoint= find(y== max(y(:))) % find the index of max point
xhigh = x(maxpoint) % this is the x value of max height
h = plot(x(maxpoint),y(maxpoint), 'r.'); % plots the max height on the graph and outputs the result
set(h, 'MarkerSize', 20); % plots h and displays dotted positions of the ball

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Answer 1

Ameer Hamza 2020-4-27

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/520991-projectile-motion-graph-error#answer_428629

在 MATLAB Online 中打开

Add this if-block at the end of for loop

grid on
drawnow
% ^ after these lines add
if y < 1
    break
end

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Ameer Hamza 2020-4-27

在 MATLAB Online 中打开

Ok. That will only happen in you set initial y < 1. If you start with higher value, it does not happen. I have added another condition to check this. Try the following updated code.

clc
clear all
close all
format long
V = input('Enter velocity: ') % user enters initial Velocity in m/s
g= input('Enter acceleration due to gravity: ') % user enters gravity acceleration in m/s^2
theta= input('Enter angle: ') % user enters angle in degrees
y0=input('Enter Initial height: ') %user Enters the initial Height in m
Fs = input('Enter constant force spring force= '); %Constant force spring force, Fs (N)
t=0:0.1:5; %Time Vector; When this is changed, the value of x changes.
% please change only to shorten the simulation time.
figure
set(gcf,'position',[50,50,1200,500])
%close all
Vx = V.*cosd(theta) % Component of X value
Vy = V.*sind(theta)
% loop that goes through to get the x and y values and plots them using the
% built in plot function and stops while time(t) is reached
flag = false;
for i= 1:length(t)
    
    %Vy = V.*cosd(theta)-g*t(i)
    
    x=Vx*t(i); %Formula to find X
    y=y0+V.*sind(theta)*t(i)-g*t(i)^2; % Formula to find Y
    
    % Find all the indices of y that are less than zero
    zeroIdx = find(y < 0);
    % If there are indices with altitude less than zero, find the first one and set the X axis limits
    if ~isempty(zeroIdx)
        finalPosition = y(zeroIdx(1));
        if(finalPosition>0)
            xlim([0, finalPosition])
        else
            xlim([finalPosition,0])
        end
    end
    % Set all altitudes less than zero to zero (can't penetrate the ground!)
    y(zeroIdx) = 0;
    
    plot(x,y,'o','MarkerFacecolor','b')
    hold all
    axis equal
    xlabel('x in meters')
    ylabel('y in meters')
    xlim([0 180]) % the second value in the brackets sets the limit for the X axis
    ylim([0 100]) % the second value in the brackets sets the limit for the Y axis
    
    grid on
    drawnow
    if (y < 1) && flag
        break
    end
    
    if y > 1
        flag = true;
    end
end
k=Fs./x;
fprintf("%i",k)
zoom on;
maxh= max(y) % find the max height by finding Y max using the max() function
maxpoint= find(y== max(y(:))) % find the index of max point
xhigh = x(maxpoint) % this is the x value of max height
h = plot(x(maxpoint),y(maxpoint), 'r.'); % plots the max height on the graph and outputs the result
set(h, 'MarkerSize', 20); % plots h and displays dotted positions of the ball

Ziad Al Malouf 2020-4-27

Thank you sooo much... it worked, mind explaining the updated if statement?..

Ameer Hamza 2020-4-27

I am glad to be of help. I added an if-condition, which breaks the for the loop when the projectile is close to ground (y < 1). In the second code, I added a new condition, then If the projectile start close to the ground (y<1), then It should not stop immediately; it should stop when the projectile is returning to ground.

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Projectile motion Graph error

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Projectile motion Graph error

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