A body of $10\, kg$ is acted by a force of $129.4\, N$ if $g = 9.8\,m/{\sec ^2}$. The acceleration of the block is $10\,m/{s^2}$. What is the coefficient of kinetic friction

When a body is moving on a surface, the force of friction is called

Consider a block and trolley system as shown in figure. If the coefficient of kinetic friction between the trolley and the surface is $0.04$ , the acceleration of the system in $\mathrm{ms}^{-2}$ is :

(Consider that the string is massless and unstretchable and the pulley is also massless and frictionless):

A block of mass $10 kg$ is moving on a rough surface as shown in figure. The frictional force acting on block is ...... $N$

A block of mass $10\, kg$ is placed on a rough horizontal surface having coefficient of friction $\,\mu  = 0.5$. If a horizontal force of $100\, N$ is acting on it, then acceleration of the block will be ....... $m/s^2$

A car having a mass of $1000\, kg$ is moving at a speed of $30\, metres/sec$. Brakes are applied to bring the car to rest. If the frictional force between the tyres and the road surface is $5000$ newtons, the car will come to rest in ........ $\sec$