A 80.0 kg person initially at rest atop a skateboard ramp that is h = 1.5 m above its lowest position. At the bottom of the ramp, the skateboarder is traveling 4.0 m/s. To the nearest joule, how much thermal energy was produced as a result of friction between the skateboard and ramp when the person reaches the bottom of the ramp?

Students in an introductory physics lab are performing an experiment with a parallel-plate capacitor made of two circular aluminum plates, each 11 cm in diameter, separated by 1.0 cm. how much charge can be added to each of the plates before a spark jumps between the two plates? for such flat electrodes, assume that value of 3×106n/c of the field causes a spark.