two people sitting on a rolling chair with little friction push off from each other so they move apart. one is 60kg and one is 40kg. if the 40kg person recoils at 3.1m/s what will the velocity id the 60kg person's recoil be in m/s

final momentum = initial momentum = 0

40 * 3.1 - 60 * v = 0
v = 40 * 3.1 / 60 = 2.07 m/s

dear answered,
Do you seriously think the heavy person ended up going faster?

The 60kg person's recoil velocity would be 4.15 m/s.