On an ice skating rink, a girl of mass 50. kg stands stationary, face to face with a boy of mass 80. kg. The children push off of one another, and the boy moves away with a velocity of -4.0 m/s. To two significant digits (the tenths place), what is the final velocity of the girl? m/s

Daughter element the new element produced along with a decay particle in a nuclear transmutation 2. half-life the substance that decays in a nuclear transmutation 3. parent element the change of one chemical element into another by nuclear decay or radioactive bombardment 4. transmutation the time required for the decay of one-half of the atoms in a sample of radioactive material