# Why won't Matlab plot anything?

4 views (last 30 days)
Akram Khandash on 25 Sep 2022
Commented: Akram Khandash on 26 Sep 2022
clear all
close all
% given values %
m = 80; %kg the mass of the sprinter%
F_x= 400; %N%
L = 100; %m the lenght of the race%
p = 1.293; %kg/m^3 the density of the air%
A = 0.45; %m^2 the cross-sectional area%
Cd = 1.2; %the drag force%
w = 0; %air velocity
time = 10;
dt = 0.1;
n = round(time/dt);
D = zeros(n,1);
a = zeros(n,1);
v = zeros(n,1);
x = zeros(n,1);
t = zeros(n,1);
a(1)= F_x/m;
v(1)=0;
x(1)=0;
D(1)=0;
t(1)=0;
for i = 1:n-1
a(i+1) = (F_x - D(i))/m;
v(i+1) = v(i) + a(i)*dt;
D(i+1) = 0.5*p*Cd*A*(v(i)-w)^2;
x(i+1) = x(i)+ v(i)*dt + 0.5*a(i)*dt^2;
t(i+1) = t(i) + dt;
if x(i+1)>=100
return
end
end
f1 = plot(t,x);
f2 = plot(t,v);
f3 = plot(t,a);
This is my code.
plot dose not show up. I hope to get help fixing it

Dyuman Joshi on 25 Sep 2022
Use break instead of return. As when you use return, any code after it won't be executed
"Be careful when you use return within conditional blocks, such as if or switch, or within loop control statements, such as for or while. When MATLAB reaches a return statement, it does not just exit the loop; it exits the script or function and returns control to the invoking program or command prompt."
m = 80; %kg the mass of the sprinter%
F_x= 400; %N%
L = 100; %m the lenght of the race%
p = 1.293; %kg/m^3 the density of the air%
A = 0.45; %m^2 the cross-sectional area%
Cd = 1.2; %the drag force%
w = 0; %air velocity
time = 10;
dt = 0.1;
n = round(time/dt);
D = zeros(n,1);
a = zeros(n,1);
v = zeros(n,1);
x = zeros(n,1);
t = zeros(n,1);
a(1)= F_x/m;
v(1)=0;
x(1)=0;
D(1)=0;
t(1)=0;
for i = 1:n-1
a(i+1) = (F_x - D(i))/m;
v(i+1) = v(i) + a(i)*dt;
D(i+1) = 0.5*p*Cd*A*(v(i)-w)^2;
x(i+1) = x(i)+ v(i)*dt + 0.5*a(i)*dt^2;
t(i+1) = t(i) + dt;
if x(i+1)>=100
break
end
end
f1 = plot(t,x);
f2 = plot(t,v);
f3 = plot(t,a);
Akram Khandash on 26 Sep 2022
thanks, its work now

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