(A) Given: $m_1 = 2 \ kg$,$m_2 = 1 \ kg$,$u_1 = 2 \ m/s$,$u_2 = 5 \ m/s$. Case $1$: Both particles move in the same direction. The velocity of the cen

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(A) Given: $m_1 = 2 \ kg$,$m_2 = 1 \ kg$,$u_1 = 2 \ m/s$,$u_2 = 5 \ m/s$. Case $1$: Both particles move in the same direction. The velocity of the centre of mass is $v_{cm} = \frac{m_1 u_1 + m_2 u_2}{m_1 + m_2} = \frac{2(2) + 1(5)}{2 + 1} = \frac{4 + 5}{3} = 3 \ m/s$. So,$v_1 = 3 \ m/s$. Case $2$: Both particles move in opposite directions. Let $u_1 = 2 \ m/s$ and $u_2 = -5 \ m/s$. The velocity of the centre of mass is $v_{cm} = \frac{m_1 u_1 + m_2 u_2}{m_1 + m_2} = \frac{2(2) + 1(-5)}{2 + 1} = \frac{4 - 5}{3} = -1/3 \ m/s$. The speed is the magnitude of velocity,so $v_2 = |-1/3| = 1/3 \ m/s$.

Class 11 Physics System of Particles and Rotational Motion Motion of Centre of Mass

Medium

Two particles of masses $2 \ kg$ and $1 \ kg$ are moving along the same line with speeds of $2 \ m/s$ and $5 \ m/s$ respectively. If both particles are moving in the same direction,the speed of the centre of mass is $v_1$. If both particles are moving in opposite directions,the speed of the centre of mass is $v_2$. Find $v_1$ and $v_2$.

A
$3 \ m/s, \ 1/3 \ m/s$
B
$1/3 \ m/s, \ 3 \ m/s$
C
$2 \ m/s, \ 1/2 \ m/s$
D
$1/2 \ m/s, \ 2 \ m/s$

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Class 11

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System of Particles and Rotational Motion

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Motion of Centre of Mass

Two bodies of masses $2\ kg$ and $4\ kg$ are moving with velocities $2\ m/s$ and $10\ m/s$ respectively along the same direction. The velocity of their centre of mass will be ......... $m/s$.

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$A$ ladder $AP$ of length $5\, m$ is inclined to a vertical wall and is slipping over a horizontal surface with a velocity of $2\, m/s$. When the end $A$ is at a distance of $3\, m$ from the wall,what is the velocity of the center of mass $(C.M.)$ of the ladder at this moment (in $, m/s$)?

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Two particles $A$ and $B$,initially at rest,move towards each other under a mutual force of attraction. At the instant when the speed of $A$ is $v$ and the speed of $B$ is $2v$,the speed of the center of mass of the system is:

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$A$ man of mass $M$ stands at one end of a plank of length $\ell$,which lies at rest on a frictionless surface. The man walks to the other end of the plank. If the mass of the plank is $3M$,what is the distance moved by the man relative to the ground?

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The figure shows a man of mass $m$ standing at the end $A$ of a trolley of mass $M$ placed at rest on a smooth horizontal surface. The man starts moving towards the end $B$ with a velocity $u_{rel}$ with respect to the trolley. The length of the trolley is $L$. Choose the correct statement.

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Two bodies of masses $2\ kg$ and $4\ kg$ are moving with velocities $2\ m/s$ and $10\ m/s$ respectively along the same direction. The velocity of their centre of mass will be ......... $m/s$.

$A$ ladder $AP$ of length $5\, m$ is inclined to a vertical wall and is slipping over a horizontal surface with a velocity of $2\, m/s$. When the end $A$ is at a distance of $3\, m$ from the wall,what is the velocity of the center of mass $(C.M.)$ of the ladder at this moment (in $, m/s$)?

Two particles $A$ and $B$,initially at rest,move towards each other under a mutual force of attraction. At the instant when the speed of $A$ is $v$ and the speed of $B$ is $2v$,the speed of the center of mass of the system is:

$A$ man of mass $M$ stands at one end of a plank of length $\ell$,which lies at rest on a frictionless surface. The man walks to the other end of the plank. If the mass of the plank is $3M$,what is the distance moved by the man relative to the ground?

The figure shows a man of mass $m$ standing at the end $A$ of a trolley of mass $M$ placed at rest on a smooth horizontal surface. The man starts moving towards the end $B$ with a velocity $u_{rel}$ with respect to the trolley. The length of the trolley is $L$. Choose the correct statement.

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