An electron (q=-e) completes half of a circular orbit of radius r around a nucleus with Q=+3e.
a. How much work is done on the electron as it moves from i to f? Give either a numerical value if you knew the radius. Justify your answer.
b. By how much does the electric potential energy change as the electron moves from i to f?
c. Is the electron's speed at f greater than, less than, or equal to its speed at i?