As explained yesterday, today was about practicing with the charge model. We were still WB’ing the practice sheet, but that went hand-in-hand with drawing a series of pictures for conduction and induction, and each student having an opportunity to charge an electroscope with each method:
Well, I really like the Hot Wheels activity for energy conservation… after all, who does not love to play with the little cars? The issue for some today was that the kinetic energy at the bottom of the ramp, had a greater value than the gravitational energy at the op of ramp… not so Hot. So is the error with the determination of the change in height or the velocity?
I think I figured out the issue. I was using a single photo gate with ‘One Gate Timing’ to get the instantaneous velocity of the car at the final height. I’ve used a single photo gate successfully over and over and over and over …. it’s one of my favorite uses of the photogate. When I run the experiment, no issues, but when some of my generals did it, they must have measured the ‘flag’ incorrectly. It is a narrow flag to give a better value for the instantaneous velocity, but even a millimeter off makes a difference when the energy values are so small to start with. Tomorrow I will try a different photogate, one with no flag needed… a Bee-Spy photogate. I am pretty sure the cars will fit through. Stay tuned…