Four days... four days!!!!????

I apparently did a number on my karma by basing a problem on dear Mr. Kirpes' suffering.  Going on day four of a fever, long story short, when you can get a flu shot for free, you really should get that flu shot.  Sooooo, uh day four of not being at school, uh...   By now, you've seen a pattern a couple of places whereby the work aka working aka energy transfer can be found by determining the area of a force v. distance graph.  For the spring, that graph is a triangle, and the area equation shakes out to be Ee=1/2k*(x)^2.  If you think about it, when you went up the stairs yesterday, you applied an average force equal to your weight-ish (Fg=mg) over a vertical displacement of delta y.  That average force would be constantish (think about the elevator doing the same thing, little bit more than Fg at the beginning, equal to Fg for the CVPM part in the middle, and a little less than Fg at the end;  long story short, it'd average out to Fg.)  So let's say you want to determine the amount of energy transfer due to friction.  As you'll no doubt recall, friction force depends only on the coefficient of friction, and the Normal force.  It does not vary with velocity.  So consider a graph of Friction force v. delta x for an object sliding to rest.  The area under the graph would be equal to the energy transferred from Ek to Eth by friction.

So apply that idea to the puck in these videos (keep in mind that good suggestion to leave mass as a a variable 'm' when it's not given, because it just might cancel out).  Grab a laptop for your group (or use your own if it's fancy) and a whiteboard for your work.  See if you can determine the coefficient of friction.

If that doesn't work, try this link
If that doesn't work, just go to the dang page and click the links yourself until it does work

What must be true of the initial speed of the puck in this follow-up video based on the distance it slides?

After the presentation of the solutions to the above problems, have at the work and energy clicker questions (Max, can you please hook up the clickers set up for everyone to use? thanks!)