Blocks sliding on top of each other w/ friction

Initial conditions :

  • Mass 1 {top} {1-20 kg} =  kg
  • Mass 2 {bottom} {1-20 kg} =  kg
  • Force of push (F) {the hand} =  Newtons
  • coeff of Static friction µS {0.2 - 0.9} =  
  • coeff of Kinetic friction µK {0.1 - 0.8} (less than µS!) =  

Push on M1 {uncheck to push on M2}

                                 

Description :

Mass M1=blue sits on top of mass M2=red. The surface under M2 is frictionless, but there is static and/or kinetic friction between M1 and M2. There can be a push force applied to either M1 or M2 (checking the box above puts the force on M1). You can set the various values above, then click the UPDATE INFO button, and then "play" the animation. (The Acceleration values for each mass are shown .. after the animation starts running.)

Questions

Refer to the Group Project paper for the questions to answer.

Non-physical behavior?
      I've tried to "stop" the animation as best I could before the two masses "completely separate", but there could be combinations of values where the masses will appear to pull apart before the animation stops (leaving the top mass "floating" sideways) ... have pity on a feeble-minded physics professor .. eventually I'll get it worked out. Until then, our equations don't change .. all we really need is the accelerations - time doesn't come in to our equations (but it is handy to animate with time).