Space explorers discover an 8.7×10^17kg asteroid that happens to have a positive charge of 4400

C. They would like to place their 3.3×10^5kg spaceship in orbit around the asteroid. Interestingly, the solar wind has given their spaceship a charge of -1.2C. What speed must their spaceship have to achieve a 7300-
km -diameter circular orbit?

I do not know how to start this problem.

4 answers

m = spaceship mass = 3.3*10^5
M = asteroid mass = 8.7*10^17
R = 7,300,000 m = 7.3*10^6 meters

F = m a = m v^2/R

F = G m M/R^2 + k |Q1| |Q2|/R^2
(both forces +, attraction)

so
v^2 = G M/R + k |Q1| |Q2|/(m R)

its actually 5.2 m/s

6.2 m/s