A man and a plank of the same mass are moving with a velocity v along positive x-axis. At the same time man jumps along negative x-axis with a velocity v with respect to ground, then the speed of the plank is:

Question

A man and a plank of the same mass are moving with a velocity v along positive x-axis. At the same time man jumps along negative x-axis with a velocity v with respect to ground, then the speed of the plank is: (A) v (B) 2 v (C) 3 v (D) none of these

Tardigrade Admin · Accepted Answer

By conservation of linear momentum (consider man and plank as system) m v+m v=m(-v)+m v prime ( v prime is the final speed of plank) v prime=3 v

Q. A man and a plank of the same mass are moving with a velocity $v$ along positive $x$ -axis. At the same time man jumps along negative $x$ -axis with a velocity $v$ with respect to ground, then the speed of the plank is:

$v$

$2 v$

$3 v$

none of these

By conservation of linear momentum (consider man and plank as system)
$m v + m v = m (- v) + m v^{'}$
( $v^{'}$ is the final speed of plank)
$v^{'} = 3 v$

Q. A man and a plank of the same mass are moving with a velocity v along positive x-axis. At the same time man jumps along negative x-axis with a velocity v with respect to ground, then the speed of the plank is:

v

2v

3v

none of these

By conservation of linear momentum (consider man and plank as system) mv+mv=m(−v)+mv′ ( v′ is the final speed of plank) v′=3v

Q. A man and a plank of the same mass are moving with a velocity $v$ along positive $x$ -axis. At the same time man jumps along negative $x$ -axis with a velocity $v$ with respect to ground, then the speed of the plank is:

$v$

$2 v$

$3 v$

By conservation of linear momentum (consider man and plank as system)
$m v + m v = m (- v) + m v^{'}$
( $v^{'}$ is the final speed of plank)
$v^{'} = 3 v$