%Fill in this code.  Don't look up lecture notes, or any other notes or books.

function zdot = myrhs(t,z,p);
r= z(1:2);  v = z(3:4);  % unpack state variables

%Unpack parameters
m = p.m; ...  % fill in as needed

rdot = v;  % first two of 4 ODES

%Various forces, pick and choose
Fg      =             % Near-earth gravity
FG      =             % Inverse-square gravity
FDL     =             % Linear drag
FDQ     =             % Quadratic drag
Fspring =              % Spring from origing
Fdash   =             % linear dashpot from origin (challenge!)

% Use one or more of the forces above or any other forces
Ftot    = ;

% LMB a.k.a. F = ma
vdot    = Ftot/m;     % second two of 4 ODEs

zdot = [rdot;vdot];
end % end of rhs function
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