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…
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
30 cm
40 cm
80 cm
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
$\Delta \mathrm{r}=\left(\frac{\mathrm{m}}{\mathrm{M}+\mathrm{m}}\right) \mathrm{l}=\left(\frac{20}{20+90}\right) \times 3.3=60 \mathrm{~cm}$