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

$A$ block of mass $10 \ kg$ is moving on a rough surface with a velocity $v = 4 \ m/s$ to the left. An external force $F = 20 \ N$ is applied to the right as shown in the figure. The coefficient of kinetic friction is $\mu = 0.6$. The frictional force acting on the block is ...... $N$.

$A$ block of mass $5 \,kg$ moving on a rough surface with a velocity of $4 \,ms^{-1}$ is stopped by friction in $2 \,s$. The coefficient of friction between the contact surfaces is (Acceleration due to gravity $g = 10 \,ms^{-2}$)

Two blocks of masses $M_1$ and $M_2$ are connected with a string passing over a pulley as shown in the figure. The block $M_1$ lies on a horizontal surface. The coefficient of friction between the block $M_1$ and the horizontal surface is $\mu$. What additional mass $m$ should be placed on the block $M_1$ so that the system does not accelerate?

$A$ bag is gently dropped on a conveyor belt moving at a speed of $2\,m/s$. The coefficient of friction between the conveyor belt and the bag is $0.4$. Initially,the bag slips on the belt before it stops slipping due to friction. The distance travelled by the bag on the belt during the slipping motion is $.....m$. [Take $g=10\,m/s^{-2}$]

$A$ car is moving along a straight horizontal road with a speed $v_0$. If the coefficient of friction between the tyres and the road is $\mu$,the shortest distance in which the car can be stopped is