Question

A MAN OF MASS M STANDS AT ONE END OF A PLANK OF LENGTH L WHICH LIES AT REST ON A FRICTIONLESS HORIZONTAL SURFACE. THE MAN WALKS TO THE OTHER END OF THE PLANK. IF THE MASS OF THE PLANK IS (M/3), THE DISTANCE THAT THE MAN MOVES RELATIVE TO THE GROUND WILL BE _________ A) L. B) L/4. C) 3L/4. D) L/3

Answer 1

initially the center of mass is at rest.
therefore the center of mass does not move in horizontal direction.
it is L/8 distance away from the end of the side of the man.
let x be the dispacement of the plank after the man walks to the other side.
then (L-x) will be the displacement of man.
let  initially the center of mass be at origin i.e xi=0.
as we said earlier ,the center of mass will not move in horizontal direction therefore the center of mass remains stationary,
xi=xf
L/8=(m(L-x)+m/3(L/2-x))/(m+m/3)    ( )

thus we get x=3L/4,
therefore the man moved L-x=L/4

Answer 2

Explanation:

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