About bugs K1,K2 normally when i run applet appear value of k1,k2 zero but when i change
Value for example k2 i change value to 1,000000 to click Play so the mass move so fast and appear
Error in x,y value beside time, about graphic when i run applet still applet finish running i look to value of x,y
And check graphic of x and y i find different but i think wrong only in y, last thing is the mass after i set value of angle and velocity
I run applet so mass move normally still end when touch another point on other side must stop but not stop continue move but no always some times stop i think is like relationship between value of angle and velocity.  
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1984.0;attach=3540[/img]