Newtons 3rd law is very nonexistent in the simulation universe. So I was interested to see this one.

When I noticed that a UK physics assessment test had lots of questions about reactive forces I tried to make a simulation in a nice simulator called Particle World. Unfortunately it is not a free program but I got permission to have a copy:

http://tupo.biz/kurser/javaapplets/Fysik/java/PW/appletstarter.html

In the starting simulation you can see many bodies with different masses and speeds in 1-dim collisions. All had identical springs to show the forces involved. You can change to the same but with English labels with [b]File>predefined>Newtons3je>8 cases speeds masses[/b]

I have a bunch of exercises to follow through but they are only in Swedish.

It is possible to Export / import simulations into this applet. And it is fun to play with. You can grab things with your mouse too and throw them around.

It ought to be easy to make something similar with Physlets or EJS.