A 45.2-kg girl is standing on a 143-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 1.56 i m/s relative to the plank.
(a) What is the velocity of the plank relative to the ice surface?
i m/s
(b) What is the girl's velocity relative to the ice surface?
i m/s