Physics question, ?

a cue ball with mass 170 g hits the stationary number 8 ball, which has mass 160 g. the cue ball and the 8 ball move with a speed of 0.2 m/s and 0.3 m/s respectively after the collision. what was the speed of the cue ball before the collision?

a) 0.2502 m/s
b) 0.4823 m/s
c) 0.5008 m/s
d) 0.5319 m/s

Four objects each with charge +2.0×10−7c are located at the corners of a square whose sides are 2.0 m long. part a what quantities can be determined using this information? check all that apply. the electric force on a charged object placed at the center of the square. the mass of each object. the total electric potential energy of the system consisting of the four charged objects. part b find the electric force on a charged object placed at the center of the square.