Modeling Simple Friction

[mptak]

Hey all. I'm embarking on a series of simple "classic" physics problems in order to pull my kids away from their angry birds and am hoping to do them in three media.....the back of the envelope (which becomes a bar napkin depending on the age and venue), algodoo (can you say awesome) and of course sketch-up and sketchy physics (most likely with some ruby embellishments). Any suggestions on how to deal with adjusting friction? My first algodoo sketch is here: The sliding and tipping glass problem.

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[blossa]

Could it work to change gravity?