WHAT would be the reason this matlab code works but does not draw the graphic?

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Laura 2023-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/1949673-what-would-be-the-reason-this-matlab-code-works-but-does-not-draw-the-graphic

回答： VBBV 2023-4-19

% Constants
G = 6.67430e-11;    % gravitational constant 
M = 5.9722e24;      % mass of Earth 
R = 6.371e6;        % radius of Earth 
% Initial conditions
y0 = 0;             % initial height
v0 = 0;             % initial velocity
% Solve differential equation
[t, v] = ode45(@(y,v) -G*M./(v*(y+R).^2), [y0, 100*R], v0);
% Plot solution
plot(t, v);
xlabel('Height (m)');
ylabel('Velocity (m/s)');
title('Gravitational Acceleration');

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Answer 1

VBBV 2023-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/1949673-what-would-be-the-reason-this-matlab-code-works-but-does-not-draw-the-graphic#answer_1218713

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The y0 and v0 values are both zero and that results in infinite value, which cannot be plotted. Give suitable values to both variables or ateast v0 since velocity of eath cannot be zero

y0 = 0; % initial height

v0 = 0; % initial velocity

G = 6.67430e-11; % gravitational constant

M = 5.9722e24; % mass of Earth

R = 6.371e6; % radius of Earth

y = -G*M./(v0*(y0+R).^2)

y = -Inf

plot(y)