The instructions were somewhat nebulous and one has to invest some time to "play" with the applet to gain full appreciation of what it can do. If used by students, better directions might be needed to understand from the outset
what they are expected to accomplish with a given click and drag procedure.
On the first applet,
the reset button does not set the time to zero (0) (or move the particle back to its initial positions) until the simulation starts to run again.
On the second simulation, it is not stated that the value of "Y" corresponds to the height of the incline. Also, an explanation of the meaning of the dots that appear on the screen while the ball is rolling down the incline may be useful, if "Motion Diagrams" have not previously been used in class.