A 46.0-kg girl is standing on a 159-kg plank. Both originally at rest on a frozen lake that constitutes a frictionless, flat surface. The girl begins to walk along the plank at a constant velocity of 1.44i hat bold m/s relative to the plank.
(a) What is the velocity of the plank relative to the ice surface?
(b) What is the girl's velocity relative to the ice surface?