kerja Posted May 12, 2009 Share Posted May 12, 2009 Hi, can someone help me with solving this thing? I'm at the exam at the mo, stuck on this one... thank you! Link to comment Share on other sites More sharing options...
timo Posted May 12, 2009 Share Posted May 12, 2009 In the exam at the moment ?!? The forum rules say something like "we do not do your homework for you". While not strictly speaking, in the sense of that message that naturally means "we will not help you cheat in an exam". Link to comment Share on other sites More sharing options...
kerja Posted May 12, 2009 Author Share Posted May 12, 2009 well, I've just stuck on the question. I've done something like that: clear all dt= 0.01; t_max=10; i_max=ceil(t_max/dt)+1; y=zeros(1,i_max); x=zeros(1,i_max); y(1)= 0; x(1)= 1; k=0; t=[0.0:dt:(i_max-1)*dt]; for i=1:i_max-1 k1=-x(i)^2+20; l1=y(i); k2=-x(i)^2+dt*l1/2-k+20; l2=y(i)+dt*k1/2; k3=-x(i)^2+dt*l2/2-k+20; l3=y(i)+dt*k2/2; k4=-x(i)^2+dt*l3-k+20; l4=y(i)+dt*k3; y(i+1)=y(i)+(dt/6)*(k1+2*k2+2*k3+k4); x(i+1)=x(i)+(dt/6)*(l1+2*l2+2*l3+l4); end figure(2) plot(t,x,'b','LineWidth',1),xlabel('t / s'),ylabel('x / m') but think that's wrong btw, the exam is opensource based. Link to comment Share on other sites More sharing options...
mooeypoo Posted May 12, 2009 Share Posted May 12, 2009 btw, the exam is opensource based. I doubt that means asking others to answer for you. In any case, now that the exam is over - we are not in the habit of answering homework (or EXAM!) questions for you. If you want homework assistance, there's a special sub-forum for that purpose, where we can review your attempts and help you understand the subject. Good luck. ~moo Link to comment Share on other sites More sharing options...
BlondeEngineer Posted May 13, 2009 Share Posted May 13, 2009 You have a double dot on top of X that means it's acceleration (a double derivative) However... X is a function of t... ooooo!!! I see your dilemma... You need Laplace Transforms, Baby!!! Link to comment Share on other sites More sharing options...
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