Calculate the maximum acceleration (in $m s ^{-2}$) of a moving car so that a body lying on the floor of the car remains stationary. The coefficient of static friction between the body and the floor is $0.15$ $\left( g =10 m s ^{-2}\right)$.

In the figure shown, a block of weight $10 \,N$ resting on a horizontal surface. The coefficient of static friction between the block and the surface ${\mu _s} = 0.4$. A force of $3.5\, N$ will keep the block in uniform motion, once it has been set in motion. A horizontal force of $3 \,N$ is applied to the block, then the block will

Why coefficient friction is considered as static friction ? 

A block of mass $2\,kg$ moving on a horizontal surface with speed of $4\,ms ^{-1}$ enters a rough surface ranging from $x =0.5\,m$ to $x =1.5\,m$. The retarding force in this range of rough surface is related to distance by $F =- kx$ where $k =12\,Nm ^{-1}$. The speed of the block as it just crosses the rough surface will be ........... $\,ms ^{-1}$

The coefficient of static friction, $\mu _s$ between block $A$ of mass $2\,kg$ and the table as shown in the figure is $0.2$. What would be the maximum mass value of block $B$ so that the two blocks $B$ so that the two blocks do not move? The string and the pulley are assumed to be smooth and masseless ....... $kg$ $(g = 10\,m/s^2)$

Aball of mass $m$ is thrown vertically upwards.Assume the force of air resistance has magnitude proportional to the velocity, and direction opposite to the velocity's. At the highest point, the ball's acceleration is