21 a 1550-kg car moving at a constant speed of (900 km/hr) Its takes (16,000W)to keep it on alevel road. How much power is required to keep the car moving at the same speed up a hill inclined at an angle of 35° with horizontal?

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.