Why won't Matlab plot anything?

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

Answer 1

[Dyuman Joshi]

Use break instead of return. As when you use return, any code after it won't be executed

From the documentation -

"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]

thanks, its work now