pulling a 15 kg mass from a bucket from a depth of 6 meters well a man shook 20 sec what was his power

What is the role of lenses in microscopy?

What happens when a rubber rod is rubbed with a piece of fur?

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.