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A 45.0-kg girl is standing on a 168-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 1.55 m/s to the right relative to the plank.

Required:
What is the velocity of the plank relative to the surface of the ice?

Respuesta :

whitneytr12

Answer:

The speed of the plank relative to the ice is:

[tex]v_{p}=-0.33\: m/s[/tex]

Explanation:

Here we can use momentum conservation. Do not forget it is relative to the ice.

[tex]m_{g}v_{g}+m_{p}v_{p}=0[/tex] (1)

Where:

  • m(g) is the mass of the girl
  • m(p) is the mass of the plank
  • v(g) is the speed of the girl
  • v(p) is the speed of the plank

Now, as we have relative velocities, we have:

[tex]v_{g/b}=v_{g}-v_{p}=1.55 \: m/s[/tex] (2)

v(g/b) is the speed of the girl relative to the plank

Solving the system of equations (1) and (2)

[tex]45v_{g}+168v_{p}=0[/tex]

[tex]v_{g}-v_{p}=1.55[/tex]

[tex]v_{p}=-0.33\: m/s[/tex]

I hope it helps you!