If an explosion occurs in a projectile,which force acts on its centre of mass?

If the overbridge is concave instead of being convex,the thrust on the road at the lowest position will be

$A$ force of $36 \, \text{dyne}$ acts on a body placed on an inclined plane making an angle of $60^{\circ}$ with the horizontal. If the mass of the body is $18 \, \text{g}$,what is the acceleration of the body in the horizontal direction?

$A$ particle of mass $7 \, kg$ moving at $5 \, m/s$ is acted upon by a variable force opposite to its initial direction of motion. The variation of force $F$ with time $t$ is shown in the graph.

$A$ vehicle without passengers is moving on a frictionless horizontal road with velocity $u$ and can be stopped in a distance $d$. Now,$40\%$ of its weight is added. If the retardation remains the same,what is the stopping distance at velocity $u$?

Two blocks ($P$ and $Q$) with masses $2 \text{ kg}$ and $1.5 \text{ kg}$ respectively are joined by a massless thread. These blocks are mounted on a frictionless pulley which is fixed on the edge of a cube $(S)$,as shown in the figure. Block $P$ is positioned on the top surface which has no friction,and block $Q$ is in contact with the side surface,which has a coefficient of friction $\mu$. The cube $(S)$ moves towards the right with an acceleration of $g/2$,where $g$ is the gravitational acceleration. During this movement,the blocks $P$ and $Q$ remain stationary relative to the cube. The value of $\mu$ is . . . . . . . (Take $g = 10 \text{ m/s}^2$)