Aball is thrown upward from the ground with an initial speed speed of 25 meters/second; at the same instant, a ball is dropped from rest from a building 15 meters high. after how long will the balls be at the same height?

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.