. Two friends are ice-skating and move towards each other with speeds of +2.3 m/s and -1.9 m/s, collide and stay holding each other. If both friends have the same mass of 30 kg, what is their final velocity?

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.