Friction — Prelims Questions

A block of mass $m = 2,\text{kg}$ is placed on a rough horizontal surface. The coefficient of static friction between the block and the surface is $\mu_s = 0.6$, and the coefficient of kinetic friction is $\mu_k = 0.4$. If a horizontal force $F = 10,\text{N}$ is applied to the block, what is the magnitude of the frictional force acting on the block? (Take $g = 10,\text{m/s}^2$)

A block is placed on an inclined plane. The angle of inclination of the plane is gradually increased. At an angle of $30^circ$, the block just begins to slide down. What is the coefficient of static friction between the block and the plane?

A $4,\text{kg}$ block is pulled horizontally by a force of $20,\text{N}$. If the coefficient of kinetic friction between the block and the surface is $0.2$, what is the acceleration of the block? (Take $g = 10,\text{m/s}^2$)

Which of the following statements about friction is INCORRECT?

A coin is placed on a rotating turntable. The coefficient of static friction between the coin and the turntable is $0.5$. If the turntable rotates at $20,\text{rad/s}$, what is the maximum distance from the center at which the coin can be placed without slipping? (Take $g = 10,\text{m/s}^2$)

A block of mass $m$ is placed on an inclined plane with an angle of inclination $\theta$. The coefficient of kinetic friction between the block and the plane is $\mu_k$. If the block slides down the plane with a constant velocity, what is the relationship between $\theta$ and $\mu_k$?