A block of mass $m$ is placed on a surface having vertical cross section given by $y=x^2 / 4$. If coefficient of friction is $0.5$ , the maximum height above the ground at which block can be placed without slipping is:

A body of mass $4\, kg$ is at rest on a horizontal table. The coefficient of friction between  the body and the table is $0.2$ . A horizontal force of $6N$ is applied on the body.  The acceleration of the body is .......... $m/s^2$

A hockey player is moving northward and suddenly turns westward with the same speed to avoid an oopponent. The force that acts on the player is

......... $m/s^2$ is magnitude of acceleration of a block moving with speed $10\,m/s$ on a rough surface if coefficient of friction is $0.2$.

A block of $1\, kg$ is stopped against a wall by applying a force $F$ perpendicular to the wall. If $\mu = 0.2$ then minimum value of $F$ will be ....... $N.$

Write advantages and disadvantages of friction. Write remedies to reduce friction.