Two spaceships are approaching each other. (a) if the speed of each is 0.9c relative to earth, what is the speed of one relative to the other? (b) if the speed of each relative to earth is 30,000 m/s (about 100 times the speed of sound), what is the speed of one relative to the other?

a charge 3q is at the origin, and a charge −2q is on the positive x axis at x=a. part a where on the x-axis would you place a third charge so it would experience no net electric force? enter an expression for the exact answer, which will involve a square-root sign. (do not enter an approximate decimal answer.)