Start with this applet. Use the cursor to move a ball to one side 
http://www.msu.edu/user/brechtjo/physics/newtonBalls/newtonBalls.html 



See this wonderful applet
http://www.loncapa.org/~mmp/kap6/cd157a.htm
INELASTIC INTERACTIONS
Most interactions between objects are said t be Inelastic wherein momentum is conserved, but not kinetic energy. Note that this is not a violation of the law of conservation of energy. In inelasatic events, some KE may be converted to heat. KE is considered "lost" not because we cannot find it but rather because we cannot retrieve it. Examples of inelastic events include moving objects colliding and sticking together, or two objects moving (or not) and springing apart. A quick calculation of KE before and after the event will confirm this. We can account for the missing energy; we just cannot get to it easily.
Sometimes the question is phrased "what fraction of the original KE is lost?" The answer to this question involves building a fraction that has a numerator and a denominator. The syntax of the question can be used as a guide building this fraction. What follows the word "of" in the question goes into the denominator; what follows the word "is"goes to the numerator. As an example, what fraction of 4 is 3? "What fraction of the original kinetic energy is lost?"becomes a fraction (KE before  KE after) / KE before. While this fraction seems ungainly, substituting masses and velocities often yield a very managab,e answer
Visit this
applet to see the law at work
http://zebu.uoregon.edu/nsf/mo.html
ELASTIC COLLISIONS
The law of conservation of momemtum applies in all interactions (collisions and explosions) in one, two, or three dimensions (all means all). Additionally, If the proper circumstances are in place, a collision can occur where kinetic energy as well as momentum is conserved. Such a collision is elastic If such an event takes place, two other equations apply and are presented below. If objects M1 and M2 move with velocities V1 & V2, respectively, before the elastic collision, then the velocities of objects after the collision are given by



It is common (though not absolutely necessary) when using these equations to let V2 = zero. This allows the reader to focus attention on each object before and after the collision.
Check out these web sites.


http://tqd.advanced.org/3042/java/linear_demo.html 

http://www.mcasco.com/p1lmc.html
http://www.sasked.gov.sk.ca/docs/physics/u5a23phy.html http://schutz.ucsc.edu/~josh/5A/book/momentum/node7.html http://theory.uwinnipeg.ca/physics/mom/node3.html http://library.advanced.org/16600/intermediate/momentum.shtml 

For another look at collisions go to http://rip.physics.unk.edu/CyberTextBook/Collision/ Try these applets to test the law of conservation of momentum http://zebu.uoregon.edu/nsf/mo.html http://www.phy.ntnu.edu.tw/~hwang/billiards/billiards.html 
A hallmark of mechanics is the consideration of word problems.
Useful relationships are published here in a page called EQUATIONS.
The reader should consult this page before attempting the problems
assigned.
Go
to homework problems
Go to problems at U Oregon
http://www.zebu.uoregon.edu/~probs/mech/collid.html
This page was last reviewed 10/16/05