A 45.0 kg girl is standing on a 159 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 1.38 m/s relative to the plank.(a) What is her velocity relative to the surface of ice?1 m/s(b) What is the velocity of the plank relative to the surface of ice?2 m/s

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nuuk nuuk · Answer 1 · 2019-12-17T10:44:53+01:00

Answer:

Explanation:

Given

Mass of girl [tex]m=45 kg[/tex]

Mass of Plank [tex]M=159 kg[/tex]

let [tex]v_p[/tex] and [tex]v_g[/tex] be the velocity of Plank and girl w.r.t ice

therefore [tex]v_{gp}=1.38 m/s[/tex]

Conserving Momentum

[tex](M+m)v_p+mv_{gp}=0[/tex]

[tex](45+159)v_p=-45\cdot v_{gp}[/tex]

[tex]v_p=-\frac{45}{204}\cdot 1.38[/tex]

[tex]v_p=-0.304 m/s[/tex]

[tex]v_{gp}=v_g-v_p=1.38[/tex]

[tex]v_g=-0.304+1.38=1.075 m/s[/tex]