$A$ body of mass $10\,kg$ is moving with an initial speed of $20\,m/s$. The body stops after $5\,s$ due to friction between the body and the floor. The value of the coefficient of friction is (Take acceleration due to gravity $g = 10\,m/s^2$)

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

The retarding acceleration of $7.35\, ms^{-2}$ due to frictional force stops a car of mass $400\, kg$ travelling on a road. The coefficient of friction between the tyre of the car and the road is

$A$ body of mass $2$ kg is moving on the ground and comes to rest after some time. The coefficient of kinetic friction between the body and the ground is $0.2$. The retardation in the body is ...... $m/s^2$.

$A$ block of mass $40 \,kg$ slides over a surface,when a mass of $4 \,kg$ is suspended through an inextensible massless string passing over a frictionless pulley as shown below. The coefficient of kinetic friction between the surface and the block is $0.02$. The acceleration of the block is ............ $m/s^2$. (Given $g = 10 \,m/s^2$.)

Determine the maximum acceleration in $m/s^2$ of the train in which a box lying on its floor will remain stationary,given that the coefficient of static friction between the box and the train's floor is $0.15$.