g A 47.3 kg girl is standing on a 162 kg plank. The plank, originally at rest, is free to slide on a frozen lake, which is a flat, frictionless surface. The girl begins to walk along the plank at a constant velocity of 1.36 m/s relative to the plank. What is her velocity relative to the ice surface

mass of the girl m₁ = 47.3 kg

mass of the plank m₂ = 162 kg

velocity of the girl with respect to surface = v₁

velocity of plank with respect to surface = v₂

v₁ + v₂ = 1.36

v₂ = 1.36 - v₁

applying conservation of momentum law to girl and plank.

m₁v₁ = m₂v₂

47.3 x v₁ = 162 x (1.36 - v₁)

47.3 v₁ = 220.32 - 162v₁

209.3 v₁ = 220.32

v₁ = 1.05 m / s