$A$ body of mass $2 \, kg$ is moving with a velocity $8 \, m/s$ on a smooth surface. If it is to be brought to rest in $4 \, seconds$,then the force to be applied is ......... $N$.

$A$ body of mass $5 \ kg$ is moving in a straight line. The relation between its displacement and time is $x = (t^3 - 2t - 10) \ m$. What is the force acting on it at the end of $5 \ s$ (in $N$)?

$A$ particle of mass $m$ is at rest at the origin at time $t = 0$. It is subjected to a force $F(t) = F_0e^{-bt}$ in the $x$ direction. Its speed $v(t)$ is depicted by which of the following curves?

Which physical quantity is represented by the first derivative of linear momentum with respect to time?

$A$ force separately produces accelerations of $18 \ m/s^2$, $9 \ m/s^2$, and $6 \ m/s^2$ in three bodies of masses $P$, $Q$, and $R$ respectively. If the same force is applied on a body of mass $P+Q+R$, then the acceleration of that body is: (in $m/s^2$)

The magnitude and direction of the acceleration produced in a body of mass $5 \text{ kg}$ when two mutually perpendicular forces $8 \text{ N}$ and $6 \text{ N}$ act on it, are respectively: