Plot a Potential Energy Graph
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I have the function U(x) = a x^2 - b x^3 for potential energy and want to plot it with all of a and b positive values. how do i plot this function?
4 Comments
Pooja Lalan
on 1 Sep 2021
Edited: Pooja Lalan
on 1 Sep 2021
fplot is used to plot a function of one variable. For instance, if U is a function of only x i.e. U(x), a and b must be constants.
a = 1;
b = 1;
U = @(x) a.*x.^2 - b.*x.^3;
fplot(U)
However, if you want to plot U as a function of a and b, you can fix x and use fsurf instead.
It is not quite clear how "with all of a and b positive values" translates to a graphic in this context. Is it an animation or some kind of a 3-D visual? Can you point to an example of something similar?
DGM
on 2 Sep 2021
"all of a and b positive values"
You do realize that's an infinite domain, right? You're going to have to settle for less than infinite.
Answers (1)
Erik Huuki
on 2 Sep 2021
Edited: Erik Huuki
on 2 Sep 2021
First solve for the roots of the equation. As long as a and b are positive there will be an answer
Turns out for this case it will always bounce off the origin and intersect at a positive value so long as a and b are positive
a = randi([1,10]);
b = randi([1,10]);
r = roots([-b,a]);
x = linspace(0,r);
y = a.*x.^2-b.*x.^3;
plot(x,y)
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