$A$ 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?

What is the maximum force $F$ (in $N$) that can be applied such that the block does not move? (Given $\mu = 1/(2\sqrt{3})$ and $m = \sqrt{3} \ kg$)

When two surfaces are coated with a lubricant,then they

$A$ block of mass $m$ is pulled along a horizontal surface by applying a force at an angle $\theta$ with the horizontal. The friction coefficient between the block and the surface is $\mu$. If the block travels at a uniform velocity,then the work done during its displacement $d$ is:

$A$ body of mass $10\,kg$ is moving with an initial speed of $20\,m/s$. The body stops after $5\,s$ due to friction between the body and the floor. The value of the coefficient of friction is (Take acceleration due to gravity $g = 10\,m/s^2$)

"When a man walks on a rough surface,the frictional force acts in the direction opposite to his motion." Is this statement correct? Give reasons.