Q130 / 160 · AP EAMCET 2024 (20 May Shift 1) · Physics

A wooden plank of mass 90 kg and length 3.3 m is floating on still water. A girl of mass 20 Kg walks from one end to the other end of the plank. The distance through which the plank moves is

  • A
    30 cm
  • B
    40 cm
  • C
    80 cm
  • Correct answer
    D
    60 cm

Solution

$\mathrm{M}=90 \mathrm{~kg}, \mathrm{l}=3.3 \mathrm{~m}, \mathrm{~m}=20 \mathrm{~kg}$ The distance by which plank moves is given by $\Delta \mathrm{r}=\left(\frac{\mathrm{m}}{\mathrm{M}+\mathrm{m}}\right) \mathrm{l}=\left(\frac{20}{20+90}\right) \times 3.3=60 \mathrm{~cm}$

Hence, the correct answer is option: 'D'.

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