For the given figure,find the acceleration of the $40\, kg$ block in $m/s^2$. (Take $g = 10\, m/s^2$)

$A$ body is moving along a rough horizontal surface with an initial velocity $6\,m/s$. If the body comes to rest after travelling $9\,m$,then the coefficient of sliding friction will be

$A$ conveyor belt is moving at a constant speed of $2\, m s^{-1}$. $A$ box is gently dropped on it. The coefficient of friction between them is $\mu = 0.5$. The distance that the box will move relative to the belt before coming to rest on it,taking $g = 10\, m s^{-2}$,is ........... $m$.

$A$ boat of mass $700 \,kg$ is travelling at a speed of $24 \,ms^{-1}$ when its engine is shut off. The magnitude of frictional force $f$ between the boat and water is given by $f = 35v$, where $v$ is the speed in $ms^{-1}$ and $f$ is in newton. Find the time taken for the speed of the boat to become $6 \,ms^{-1}$. (in $\,s$)

$A$ block is thrown with a velocity of $2 \, m/s$ (relative to the ground) on a belt,which is moving with a velocity of $4 \, m/s$ in the opposite direction of the initial velocity of the block. If the block stops slipping on the belt after $4 \, s$ of throwing,then choose the correct statement$(s)$:

Determine the maximum acceleration in $m/s^2$ of the train in which a box lying on its floor will remain stationary, given that the coefficient of static friction between the box and the train's floor is $0.15$. (Take $g = 10 \ m/s^2$)