Here, as the charge is uniformly distributed in the sphere, we will consider s as an area of the sphere which is, s=4πr2 and r is radius of the gaussian surface shown in the figure above. From this, it can be seen that
Answer:Twice of given mass
Explanation:
Given
Two Particles of Equal mass placed at the base of an equilateral Triangle
let mass of two equal masses be m and third mass be m'
Taking one of the masses at origin
Therefore co-ordinates of first mass be (0,0)
Co-ordinates of other equal mass is (a,0)
if a is the length of triangle
co-ordinates of final mass 
Given its center of mass is at midway between base and third vertex therefore






I think your best bet would be.
It acts in the direction opposite of the motion