based on an earlier work by Paco and lookang

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=831.0

Thanks To Professor Fu-Kwun Hwang for guidance and Professor Francisco Esquembre for EJS and the open source digital library source codes.

special mention to engrg1 for the research done on the spring force model for all cases of e.

**Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop.**This work is licensed under a Creative Commons Attribution 2.5 Taiwan License

- Please feel free to post your ideas about how to use the simulation for better teaching and learning.
- Post questions to be asked to help students to think, to explore.
- Upload worksheets as attached files to share with more users.

the codes by engrg1 was especially useful for this final version

public double impactForce (double xa,double xb, double va ,double vb){

double f;

double y;

double x;

double z;

double a;

a=0;

// using the impact force equaion provided by Objalvo and Cohen ,1 1997

// Damping coefficient based on Brach, 1991a

// Formula can be found Pg 3 of http://www.brachengineering.com/publications/SAE%202003-01-0491.pdf

// this equation is not perfect and can only give a good estimate of the coefficient of resistution

if (es>0.05) {

x =Math.log(es)*Math.log(es);

z = Math.sqrt( x/( Math.PI* Math.PI+x));

} else z=1;

if(xa

else

f = klinear*(L-(xa-xb)); // change to 2*L by lookang

y = mass1*mass2/(mass1+mass2);

if(Math.abs(xa-xb)

}

s_z = "a= " + double2String(a,1000) +"size= " + double2String(2*radius1,1000) ;

return a;

}