function dxdt = bot_susp_1d(t, xin, m, k, c, tspan, ground, groundp)
%UNTITLED2 Summary of this function goes here
%   state xin = [ x(t) x'(t) y(t) y'(t) L(t) L'(t)]
    g = 9.8;

    % Divide up state into named variables
    x = xin(1);
    xp = xin(2); % dxdt(1)

    % get y(t) and y'(t)
    y  = interp1(tspan, ground, t ,'cubic');
    yp = interp1(tspan, groundp, t ,'cubic');

    % Dynamics equation, mass-spring-damper
    xpp = (c*yp + k*y - (c*xp + k*x + m*g))/m;  %dxdt(2)

    dxdt = [ xp ; xpp ];
end