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 个评论
darova
2021-9-1
Did you try plot? Can you attach your code?
Allen Ruff
2021-9-1
Pooja Lalan
2021-9-1
编辑：Pooja Lalan
2021-9-1
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
2021-9-2
"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.
回答（1 个）
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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