Assume Earth and a cloud layer 0.900 Km above the Earth can be treated as plates of a parallel-plate capacitor. a. If the cloud layer has an area of 2.00 × 104 m2, what is the capacitance?
b. If an electric field strength of 2.0 × 105 N/C causes the air to conduct charge (lightning), what charge can the cloud hold?
c. Describe what must happen to its molecules for air to conduct electricity.

Two cannon balls weighing 18 kg and 24 kg are chained together and fired horizontally with a velocity of 165 m/s from the top of a 21-m wall. the chain breaks during the flight of the cannonballs and the 18-kg cannonball strikes the ground at t = 1.5 s, at a distance of 240 m from the foot of the wall, and 7 m to the right of the line of fire. determine the position of the other cannonball at that instant. neglect the resistance of the air.