Spring Block with Friction Simulator
Pressing the start button below will bring up a seperate window to run 
the Spring Block with Friction Simulator.  This can sometimes take several minutes.  
However, once you have run one simulation, subsequent simulations should 
load much faster.
NOTE: This is still a BETA version of the software.  
The program is known to be stable but there are still some interface 
improvements to be made.