A 50.0-g ball of copper has a net charge of 2.00μC. What fraction of the copper's electrons has been removed? (Each copper atom has 29 protons, and copper has an atomic mass of 63.5.) Atomic Mass Unit = 1.660 × 10 27 kg/u 10.000 × 10^23 atoms 4.739 × 10^23 atoms 6.779 × 10^23 atoms 8.759 × 10^23 atoms
Suppose a car travels 108 km at a speed of 30.0 m/s, and uses 2.0 gal of gasoline. Only 30% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. (The energy content of gasoline is about 140 MJ/gal.) What is the magnitude of the force exerted to keep the car moving at constant speed? 650 N 888 N 666 N 778 N