MCQ
A $500\,kg$ boat is $9\,m$ long and is floating without motion on still water. A man of mass $100\,kg$ is at one end and if he runs to the other end of the boat and stops, the displacement of the boat is
  • A
    $1.5\,m$ in the directin of displacement of the man
  • B
    $0.75\,m$ in the directin of displacement of the man
  • $1.5\,m$ in the direction opposite to the displacement of the man
  • D
    $0.75\,m$ in the direction opposite to the displacement of the man

Answer

Correct option: C.
$1.5\,m$ in the direction opposite to the displacement of the man
c
Given that the system is initially at rest,

$\text { ie., } \quad \vec{\mathrm{V}}_{\mathrm{CM}}=0$

$\frac{m_{1} \vec{v}_{1}+m_{2} \vec{v}_{2}}{m_{1}+m_{2}}=0$

or         $\text { or } \quad \mathrm{m}_{1} \vec{\mathrm{v}}_{1}+\mathrm{m}_{2} \vec{\mathrm{v}}_{2}=0$

Or       $\mathrm{m}_{1} \frac{\Delta \overrightarrow{\mathrm{r}}_{1}}{\Delta \mathrm{t}}+\mathrm{m}_{2} \frac{\Delta \vec{\mathrm{r}}_{2}}{\Delta \mathrm{t}}=0$

$\mathrm{or}$          $\mathrm{m}_{1} \Delta \overrightarrow{\mathrm{r}}_{1}+\mathrm{m}_{2} \Delta \overrightarrow{\mathrm{r}}_{2}=0$

Now here, in boat-man system if the man

moves towards right the boat moves towards left.

$\therefore$   $\mathrm{m}_{\mathrm{1}} \Delta \mathrm{r}_{\mathrm{1}}=\mathrm{m}_{2} \Delta \mathrm{r}_{2}$          $...(i)$

$\left(\because \Delta \mathrm{r}_{\mathrm{1}} \text { is opposite to } \Delta \mathrm{r}_{2}\right)$

If $\Delta \mathrm{r}_{2}$ is the displacement of boat relative to shore, then the displacement of man relative to

shore would be $\left(9-\Delta \mathrm{r}_{2}\right)$

$\text { i.e., } \quad \Delta r_{1}=9-\Delta r_{2}$        $...(ii)$

From $(i)$ and $(i i)$

$\mathrm{m}_{1}\left(9-\Delta \mathrm{r}_{2}\right)=\mathrm{m}_{2} \Delta \mathrm{r}_{2}$

$\text { or } \quad 100\left(9-\Delta r_{2}\right)=500 \Delta r_{2}$

$\Delta r_{2}=\frac{100 \times 9}{600}=1.5 \mathrm{m}$

ie. Boat moves $1.5 \mathrm{m}$ relative to shore in the

direction opposite to the displacement of man.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

Two projectiles are thrown simultaneously in the same plane from the same point. If their velocities are $v_1$ and $v_2$ at angles $\theta _1$ and $\theta_2$ respectively from the horizontal, then answer the following question

The trajectory of particle $1$ with respect to particle $2$ will be

Projection of vector $\vec A$ on $\vec B$ is
A cube of aluminium of sides $0.1\, m$ is subjected to a shearing force of $100\, N$. The top face of the cube is displaced through $0.02 \,cm$ with respect to the bottom face. The shearing strain would be
Two uniform solid spheres having unequal masses and unequal radii are released from rest from the same height on a rough incline. If the spheres roll without slipping:
Which of the following quantities are always negative in a $SHM$
The 'Kangri' is an earthen pot used to stay warm in Kashmir during the winter months. Assume that the 'Kangri' is spherical and of surface area $7 \times 10^{-2} \,m ^{2}$. It contains $300 g$ of a mixture of coal, wood and leaves with calorific value of $30 \,kJ / g$ (and provides heat with $10 \%$ efficiency). The surface temperature of the 'Kangri' is $60^{\circ} C$ and the room temperature is $0^{\circ} C$. Then, a reasonable estimate for the duration $t$ (in h) that the 'Kangri' heat will last is (take the 'Kangri' to be a black body)
A particle moves under the effect of a force $F = Cx$ from $x = 0$ to $x = {x_1}$. The work done in the process is
A bead is free to slide down a smooth wire tightly stretched between points $A$ and $B$ on a vertical circle. If the bead starts from rest at $A$, the highest point on the circle
Two particles having mass $M$ and $m$ are moving in a circular path having radius $R$ and $r$. If their time period are same then the ratio of angular velocity will be
An experiment is carried on a fixed amount of gas at different temperatures and at high pressure such that it deviates from the ideal gas behaviour. The variation of $\frac{{PV}}{{RT}}$ with $P$ is shown in the diagram. The correct variation will correspond to