A block of mass $M = 5\,kg$ is resting on a rough horizontal surface for which the coefficient of friction is $0.2$. When a force $F = 40\,\,N$ is applied, the acceleration of the block will be  ........ $m/\sec^2$ $(g = 10\,\,m/{\sec^2})$

An insect crawls up a hemispherical surface very slowly. The coefficient of friction between the insect and the surface is $1/3$. If the line joining the centre of the hemispherical surface to the insect makes an angle $\alpha $ with the vertical, the maximum possible value of $\alpha $ so that the insect does not slip is given by

A car accelerates on a horizontal road due to force exerted by

Two bodies $A$ and $B$ of masses $5 kg$ and $10 kg$ in contact with each other rest on a table against a rigid wall. The coefficient of friction between the bodies and the table is $0.15$. A force of 200 $N$ is applied hortzontally to $A$. What are $(a)$ the reaction of the partition $(b)$ the action-reaction forces between $A$ and $B ?$ What happens when the wall is removed? Does the answer to $(b)$ change, when the bodies are in motion? Ignore the difference between $\mu_{ s }$ and $\mu_{ k }$

It is difficult to move a cycle with brakes on because