This question is from previous year.
A man of mass 30 kg is standing at one end of stationary floating plank of mass 40 kg . The length of the plank is 4 m. If man moves to other end of the plank then what will be the distance by which plank will move?

Asked by Kb Aulakh | 1st May, 2015, 07:45: PM

Expert Answer:

begin mathsize 12px style straight A space man space of space mass space 30 space kg space is space standing space at space one space end space of space stationary space floating space plank space of space mass space 40 space kg space. space The space length space of space the space plank space is space 4 space straight m. space If space man space moves space to space other space end space of space the space plank space then space what space will space be space the space distance space by space which space plank space will space move Mass space of space man space equals space 30 space kg Mass space of space plank space equals space 40 space kg Let space man space is space standing space at space the space starting space of space plank space comma space at space straight x space equals space 0 end space of space plank comma space straight x space equals space 4 CM space of space man space is space at space straight x equals 0 space CM space of space plank space is space at space straight x equals 4 divided by 2 space equals space 2 CM space of space system space equals space space fraction numerator 30 space cross times 0 space plus space 40 space cross times space 2 space over denominator 30 space plus space 40 end fraction space equals space 1.143 space straight m space Consider space man space walking space to space one space end space to space other space and space complet space straight a space distance space straight s. CM space of space man space is space at space straight x equals straight s space Hence comma space the space CM space of space plank space will space shift space to space left parenthesis 4 minus straight s right parenthesis space towards space left comma space CM space of space plank space is space at space equals space left square bracket 2 space minus space left parenthesis 4 minus straight s right parenthesis right square bracket space equals space left parenthesis straight s minus 2 right parenthesis space space CM space of space system space does space not space space change space its space position space as space space there space is space no space external space force. space space 1.143 space equals space fraction numerator 30 space cross times space straight s space plus space 40 space cross times space left parenthesis straight s minus 2 right parenthesis space over denominator 30 space plus space 40 end fraction space space space space 1.143 space cross times space open parentheses 30 space plus space 40 close parentheses space equals space 30 space straight s plus 40 space straight s space minus space 80 80 space plus space 80 space equals space 70 space straight s straight s space equals space 2.286 space straight m space space space space space space space space space space space space space space space space space space space space space end style
The distance by which plank will move is 2.286 m

Answered by Priyanka Kumbhar | 4th May, 2015, 03:47: PM

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