$A$ body of mass $2 \, kg$ moving on a horizontal surface with an initial velocity of $4 \, m/s$ comes to rest after $2 \, s$. If one wants to keep this body moving on the same surface with a constant velocity of $4 \, m/s$,the force required is ........ $N$.

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:

$A$ block is projected with speed $20 \,m/s$ on a rough horizontal surface. The coefficient of friction $(\mu)$ between the surfaces varies with time $(t)$ as shown in the figure. The speed of the body at the end of $4 \,s$ will be ............ $m/s$ $(g = 10 \,m/s^2)$.

$A$ spring-block system is placed on a rough horizontal floor. The block is pulled towards the right to give the spring some elongation and then released. The block will have maximum velocity when:

Which one of the following statements is correct?

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