$A$ body of $10\, kg$ is acted upon by a force of $129.4\, N$. If $g = 9.8\, m/s^2$ and the acceleration of the block is $10\, m/s^2$,what is the coefficient of kinetic friction?

$A$ particle of mass $M$ moves along a horizontal $x$-axis from $x=0$ to $x=L$. The coefficient of kinetic friction varies as a function of $x$ as $\mu(x) = \mu_0 - \alpha x$, where $\mu_0$ and $\alpha$ are constants of appropriate dimensions, such that $\mu(L)=0$. The total work done by the frictional force during the motion is $n\mu_0 MgL$, where $g$ is the acceleration due to gravity. The value of $n$ is:

$A$ $60\, kg$ body is pushed with just enough force to start it moving across a floor and the same force continues to act afterwards. The coefficient of static friction and sliding friction are $0.5$ and $0.4$ respectively. The acceleration of the body is ........ $m/s^2$. (Take $g = 10\, m/s^2$)

$A$ block of mass $10\, kg$ moving at $10\, m/s$ is released to slide on a rough surface having a coefficient of friction $0.2$. It will stop after travelling a distance of ........ $m$.

$A$ block of mass $M$ is moving on a rough horizontal surface with momentum $P$. The coefficient of friction between the block and the surface is $\mu$. The distance covered by the block before it stops is $[g = \text{acceleration due to gravity}]$.

$A$ block of mass $40 \,kg$ slides over a surface,when a mass of $4 \,kg$ is suspended through an inextensible massless string passing over a frictionless pulley as shown below. The coefficient of kinetic friction between the surface and the block is $0.02$. The acceleration of the block is ............ $m/s^2$. (Given $g = 10 \,m/s^2$.)