A 3.1g Ball makes a perfect inelastic collision with a second ball which is at rest. If the combined mass moves at a velocity of a quarter the original velocity Of the 3.1g ball, What is the mass of the second ball in grams?
3.1v = (3.1+m)(v/4)
3.1*4 = 3.1+m
m = 3.1*3 = 9.3g