How to make the balls in this program organize and settle at the top of the box instead of leaving it

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function y = atoms(x)
clc
n = 25; % no. of atoms
dt = 0.1; % time
ma=1;
mb=1;
x0=[0 0 0 0];
l=200;
p = rand(n,2)*0.5*l;
v = rand(n,2)+.5;
r=0.5;
for tt=1:5000
plot(p(:,1),p(:,2),'O', 'MarkerFaceColor', 'b');
axis([0 l 0 l])
drawnow;
for i = 1 : n
if p(i, 1) < 0
v(i, 1) =- v(i, 1);
end
if p(i, 1) > l
v(i, 1) = -v(i, 1);
end
if p(i, 2) < 0
v(i, 2) = v(i, 2);
end
end
for i = 1 : n
for j = i + 1 : n
d = sqrt((p(i, 1) - p(j, 1)) ^ 2 + (p(i, 2) - p(j, 2)) ^ 2);
if d < r
va = sqrt(v(i,1)^2 + v(i,2)^2);
vb = sqrt(v(j,1)^2 + v(j,2)^2);
gama = atan((p(i,2)-p(j,2))/(p(i,1)-p(j,1)));
alpha = atan2(v(i,1),v(i,2)) - gama;
beta = atan2(v(j,1),v(j,2)) - gama;
[x,fval ] = fsolve(@gh,x0);
v(i,1)=x(1)*cos(x(3)+gama);
v(i,2)=x(1)*sin(x(3)+gama);
v(j,1)=x(2)*cos(x(4)+gama);
v(j,2)=x(2)*sin(x(4)+gama);
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
end
end
end
p=p+v*dt;
end
function y = gh(x)
e = 1;
y = [ma*va*cos(alpha) + mb*vb*cos(beta) - ma*x(1)*cos(x(3)) - mb*x(2)*cos(x(4));
va*sin(alpha) - x(1)*sin(x(3));
vb*sin(beta) - x(2)*sin(x(4));
x(1)*cos(x(3)) - x(2)*cos(x(4)) - e*(va*cos(alpha) - vb*cos(beta))];
end
end

Answers (3)

KSSV
KSSV on 16 Mar 2018
Edited: KSSV on 16 Mar 2018
function y = atoms()
n = 25; % no. of atoms
dt = 0.1; % time
ma=1;
mb=1;
x0=[0 0 0 0];
l=200;
p = rand(n,2)*0.5*l;
v = rand(n,2)+.5;
r=0.5;
for tt=1:5000
idx = abs(p(:,2)-l)<=1 ; % added this line
p(idx,2) = l ; % added this line
plot(p(:,1),p(:,2),'O', 'MarkerFaceColor', 'b');
axis([0 l 0 l])
drawnow;
for i = 1 : n
if p(i, 1) < 0
v(i, 1) =- v(i, 1);
end
if p(i, 1) > l
v(i, 1) = -v(i, 1);
end
if p(i, 2) < 0
v(i, 2) = v(i, 2);
end
end
for i = 1 : n
for j = i + 1 : n
d = sqrt((p(i, 1) - p(j, 1)) ^ 2 + (p(i, 2) - p(j, 2)) ^ 2);
if d < r
va = sqrt(v(i,1)^2 + v(i,2)^2);
vb = sqrt(v(j,1)^2 + v(j,2)^2);
gama = atan((p(i,2)-p(j,2))/(p(i,1)-p(j,1)));
alpha = atan2(v(i,1),v(i,2)) - gama;
beta = atan2(v(j,1),v(j,2)) - gama;
[x,fval ] = fsolve(@gh,x0);
v(i,1)=x(1)*cos(x(3)+gama);
v(i,2)=x(1)*sin(x(3)+gama);
v(j,1)=x(2)*cos(x(4)+gama);
v(j,2)=x(2)*sin(x(4)+gama);
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
p(i,1)=p(i,1)+v(i,1)*dt;
p(i,2)=p(i,2)+v(i,2)*dt;
p(j,1)=p(j,1)+v(j,1)*dt;
p(j,2)=p(j,2)+v(j,2)*dt;
end
end
end
p=p+v*dt;
end
function y = gh(x)
e = 1;
y = [ma*va*cos(alpha) + mb*vb*cos(beta) - ma*x(1)*cos(x(3)) - mb*x(2)*cos(x(4));
va*sin(alpha) - x(1)*sin(x(3));
vb*sin(beta) - x(2)*sin(x(4));
x(1)*cos(x(3)) - x(2)*cos(x(4)) - e*(va*cos(alpha) - vb*cos(beta))];
end
end

zina shadidi
zina shadidi on 17 Mar 2018
Hi KSSv
Let me ask you please .what if we want to line the balls in more than one row

zina shadidi
zina shadidi on 21 Mar 2018
The two lines that you added makes The balls lined up at the top of the figure in a row
Now if we want the balls to line up in more than one row, ???

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