A 45.0 kg girl is standing on a 160 kgplank. The plank, originally at rest, is f

Question

A 45.0 kg girl is standing on a 160 kgplank. The plank, originally at rest, is free to slide on a frozenlake, which is a flat, frictionless surface. The girl begins towalk along the plank at a constant velocity of 1.55 m/s relative to the plank. (a) What is her velocity relative to thesurface of ice?
1 m/s

(b) What is the velocity of the plank relative to the surface ofice?
2 m/s (a) What is her velocity relative to thesurface of ice?
1 m/s

(b) What is the velocity of the plank relative to the surface ofice?
2 m/s

Explanation / Answer

Givne that the mass of the girl is  Mg = 45 kg                              mass of the plank is Mp = 160 kg           Thevelocity of the girl relative to the plank is Vgp = V1 + V2 =1.55   -------(1)               -------------------------------------------------------------------                    From the conservation ofmomentum               intiial momentum = final momentum                      Mg*V1 = Mp*V2                       Mg*(1.55m/s - V2) = Mp*V2       then we get V2 = --------- m/s        This is th eplankvelocity relative to the ice .            substitude the value of the V2 in the equation (1) we get the valueof velocity fo the girl relative to the ice   V1 = --------- m/s

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