$A$ 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 ....... $N$.

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:

$A$ block of mass $0.5 \ kg$ is at rest on a horizontal table. The coefficient of kinetic friction between the table and the block is $0.2$. If a horizontal force of $5 \ N$ is applied on the block,the kinetic energy of the block in a time of $4 \ s$ is (Acceleration due to gravity $= 10 \ m/s^2$). (in $J$)

$A$ body of mass $10 \,kg$ is kept on a rough horizontal surface with a coefficient of friction of $0.3$. If a horizontal force of $50 \,N$ is applied to the body, then the acceleration of the body is (Acceleration due to gravity $= 10 \,ms^{-2}$) (in $\,ms^{-2}$)

$A$ block of mass $m$ slides along a floor while a force of magnitude $F$ is applied to it at an angle $\theta$ as shown in the figure. The coefficient of kinetic friction is $\mu_{K}$. Then,the block's acceleration $a$ is given by: ($g$ is acceleration due to gravity)