$A$ 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 $m/s^2$)

$A$ particle of mass $m$ at rest is acted upon by a force $P$ for a time $t$. Its kinetic energy after an interval $t$ is

If a bullet of mass $5 \,g$ moving with velocity $100 \,m/s$ penetrates a wooden block up to $6 \,cm$,then the average force imposed by the bullet on the block is ........... $N$.

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

$A$ force of $6 \; N$ acts on a body at rest and of mass $1 \; kg$. During this time,the body attains a velocity of $30 \; m/s$. The time for which the force acts on the body is ..... $seconds$.

$A$ force $\vec{F_1}$ of magnitude $4 \ N$ acts on an object of mass $1 \ kg$ at the origin in a direction $30^{\circ}$ above the positive $x$-axis. $A$ second force $\vec{F_2}$ of magnitude $4 \ N$ acts on the same object in the direction of the positive $y$-axis. The magnitude of the acceleration of the object is nearly: (in $m \ s^{-2}$)