Q. Two friends, Al and Jo, have a combined mass of 177kg. At an ice skating rink they stand close together on skates, at rest and facing each other, with a compressed spring between them. The spring is kept from pushing them apart, because they are holding each other. While they release their arms, Al moves off in one direction at a speed of 0.910 m/s, even as Jo moves off in the opposite direction at a speed of 1.27m/s. assuming that friction is negligible, find out Al's mass.