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Need help fixing my ODE45 script

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Stevon Kline
Stevon Kline 2019-11-1
评论： Stevon Kline 2019-11-2
My teacher tried helping me build this code for a falling object with resistance. (We did it on paper since we didn't have a computer near at the time.) Given only the acceleration a = g+kv2. With y(0) = 1000, and v(0) = 0. Need to find the time, and velocity when object hits the ground.
I'm getting empty sets as my outputs....suggestions?
h = 1000;
t0 = 0; tfinal = 15;
tspan = [t0,tfinal];
options = odeset('Events',@landing);
[t,y,te,ye,ie] = ode45(@drag,tspan,[h;0],options);
function dydt = drag(t,y)
k = 1/10;
g = 9.8;
dydt = [-y(2); g + k*-(y(2)).^2];
end
function [check,stop,direction]=landing(t,y)
check = y(1);
stop = 1;
direction=0;
end

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Takumi
Takumi 2019-11-1
Since you want to detect when the position becomes zero, the correct description is as follows.
check = y(1);
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Takumi
Takumi 2019-11-1
Change the value of tfinal to about 150 seconds (it takes about 100 seconds to hit the ground) and check the value of te and ye (2) when the calculation is complete .These are the time and velocity when the object hits the ground respectively.

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