A body is moving down a long inclined plane of slope $370$. The coefficient of friction between the body and plane varies as $\mu=0.3 x$, where $x$ is distance travelled down the plane. The body will have maximum speed. $\left(\sin 37{ }^{\circ}=\frac{3}{5}\right.$ and $\left.g=10\,m / s ^2\right)$

Consider a block and trolley system as shown in figure. If the coefficient of kinetic friction between the trolley and the surface is $0.04$ , the acceleration of the system in $\mathrm{ms}^{-2}$ is :

(Consider that the string is massless and unstretchable and the pulley is also massless and frictionless):

A block of mass $M$ placed on rough surface of coefficient of friction equal to $3$ . If $F$ is the $(4/5)$ of the minimum force required to just move. Find out the force exerted by ground on the block

A block is placed on a rough horizontal plane. A time dependent horizontal force $F = Kt$ acts on the block. Here $K$ is a positive constant. Acceleration-time graph of the block is

A block of mass $5$ kg lies on a rough horizontal table. A force of $19.6\, N$ is enough to keep the body sliding at uniform velocity. The coefficient of sliding friction is

When a body is moving on a surface, the force of friction is called