Friction

A block is at rest on an inclined plane making an angle $\alpha$ with the horizontal. As the angle $\alpha$ of the inclination is increased, the block just starts slipping when the angle of inclination becomes $\theta$. Then the coefficient of static friction between the block and the surface of the inclined plane is

If ${\mu }_s, {\mu }_k$ and ${\mu }_r$ are coefficients of static friction, sliding friction and rolling friction, then

The force required to just move a body up the inclined plane is double the force required to just prevent the body from sliding down the plane. The coefficient of friction is $\mu .$ The inclination $\theta$ of the plane is

A horizontal force of $10 \mathrm{N}$ is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is $0.2$. The weight of the block is

A weight $W$ rests on a rough horizontal plane. If the angle of friction be $\theta$, the least horizontal force that will move the body along the plane will be

A body of mass $2 \mathrm{kg}$ is placed on a horizontal surface having kinetic friction $0.4$ and static friction $0.5$. If the force applied on the body is $2.5 \mathrm{N}$, then the frictional force acting on the body will be $\left[\mathrm{g}=10 \mathrm{m} {\mathrm{s}}^{-2}\right]$

Starting from rest, a body slides down a $45°$ inclined plane in twice the time it takes to slide down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is:

A block of mass $1 \mathrm{kg}$ lies on a horizontal in a truck. The coefficient of static friction between the block and the surface is $0.6$ if the acceleration of the truck is $5 \mathrm{m} {\mathrm{s}}^{-2}$. The frictional force acting on the block is

An eraser weighing $1$ $\mathrm{newton}$ is pressed against a vertical blackboard with a normal force of $5$ $\mathrm{newton}$. The coefficient of friction $\mu$ between eraser and blackboard is approximately $0.4$. The force along the blackboard to move the eraser is

What is the maximum value of the force $F$ such that the block shown in the arrangement does not move?

A body of mass $M$ is kept on a rough horizontal surface (friction coefficient $\mu$). A person is trying to pull the body by applying a horizontal force but the body is not moving. The force by the surface on the body is $F$, then

A block rests on a rough inclined plane making an angle of $30°$ with the horizontal. The coefficient of static friction between the block and the plane is $0.8$. If the frictional force on the block is $10 \mathrm{N}$, the mass of the block (in $\mathrm{kg}$) is (Take $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)

A marble block of mass $2 \mathrm{kg}$ lying on an ice, when given a velocity of $6 \mathrm{m} {\mathrm{s}}^{-1}$ is stopped by friction in $10 \mathrm{s}$. Then the coefficient of friction is $(g=10 \mathrm{m} {\mathrm{s}}^{-2})$

A block $\mathrm{B}$ is pushed momentarily along a horizontal surface with an initial velocity $v$. If $\mu$ is the coefficient of sliding friction between $\mathrm{B}$ and the surface, block $\mathrm{B}$ will come to rest after a time

Consider a car moving along a straight horizontal road with a speed of $72 \mathrm{km} {\mathrm{h}}^{-1}$. If the coefficient of static friction between the tyres and the road is $0.5$, the shortest distance in which the car can be stopped is (Taking $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)

Starting from the rest, a body slides down a $45°$ inclined plane in twice the time it takes to slide down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is

A conveyor belt is moving at a constant speed of $2 \mathrm{m} {\mathrm{s}}^{-1}$. A box is gently dropped on it. The coefficient of friction between them is $\mu =0.5$. The distance that the box will move relative to belt before coming to rest on it taking $g=10 \mathrm{m} {\mathrm{s}}^{-2}$, is

A marble block of mass $2 \mathrm{kg}$ lying on ice when given a velocity of $6 \mathrm{m} {\mathrm{s}}^{-1}$ is stopped by friction in $10 \mathrm{s}$. Then the coefficient of friction is (Take $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)

A block is moving on a horizontal rough surface. The coefficient of friction between their two surfaces in contact is $0.2$. The angle of friction is:

The maximum speed of a car on a road having turn of radius $30 \mathrm{m}$, if the coefficient of friction between the tyres and the road is $0.4$ will be,