syms omega V0 real
syms r(t) v(t)
assume(omega>0); assume(V0>0);
diffeq = diff(r(t),t,2) - r(t)*omega^2 == 0;
v(t) = diff(r(t),t);
IC = [r(0)==0,v(0)==V0];
sol = simplify(dsolve(diffeq,IC,symvar('r(t)')))
sol_with_nums = subs(sol,[omega,V0],[2*pi,0.05]);
fplot(sol_with_nums,[0,1],'Linewidth',2,'Color',[1,0,0])
%ylim([0 1])
set(gca,'FontSize',14)
xlabel('Time (s)')
ylabel('r(t) (m)')
grid on