$A$ block of mass $4\,kg$ is placed on a rough horizontal plane. $A$ time-dependent force $F = kt^2$ acts on the block,where $k = 2\,N/s^2$. The coefficient of friction is $\mu = 0.8$. The force of friction between the block and the plane at $t = 2\,s$ is ....... $N$.

$A$ body of mass $m$ moves with a velocity $v$ on a surface whose friction coefficient is $\mu$. If the body covers a distance $s$ before coming to rest,what is the initial velocity $v$?

Two masses $m_1 = 10 \text{ kg}$ and $m_2 = 20 \text{ kg}$ are connected by an inextensible string over a frictionless pulley,as shown in the figure. The coefficient of friction of the horizontal surface is $\mu = 0.15$. The minimum mass $m$ that should be placed on top of $m_2$ to stop the motion is:

When two surfaces are coated with a lubricant,then they

$A$ marble block of mass $2 \, kg$ lying on ice,when given a velocity of $6 \, m/s$,is stopped by friction in $10 \, s$. The coefficient of friction is:

What is the angle between the instantaneous velocity and the friction force of an object moving on a rough surface (in $^{\circ}$)?