Work done by a frictional force is

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

Block $A$ of mass $m$ and block $B$ of mass $M$ are connected by a massless spring over a pulley on a rough plane with coefficient of friction $\mu$. $A$ force $F$ is applied on block $A$ to the left. Find the minimum value of $M$ to move the block $A$ towards the right.

$A$ ball of mass $2 \ kg$ is moving in $xy$-plane with a potential energy given as $U=(12x + 16y) \ J$, where $x$ and $y$ are in metres. Assume the initial position of the ball at $t=0$ is at the origin $(0,0)$ and it is moving with a velocity of $(15 \hat{i} + 20 \hat{j}) \ m/s$. Identify the correct statement.

$A$ block of mass $M = 10\,kg$ rests on a horizontal table. The coefficient of friction between the block and the table is $\mu = 0.05.$ When hit by a bullet of mass $m = 50\,g$ moving with speed $v,$ which gets embedded in it,the block moves and comes to a stop after moving a distance of $2\,m$ on the table. If a freely falling object were to acquire speed $\frac{v}{10}$ after being dropped from height $H,$ then neglecting energy losses and taking $g = 10\,m/s^2,$ the value of $H$ is close to ................. $km$.

$A$ particle of mass $m$ falls from rest through a resistive medium having a resistive force, $F = -kv$, where $v$ is the velocity of the particle and $k$ is a constant. Which of the following graphs represents velocity $(v)$ versus time $(t)$?