Which of the following statements is correct?

$A$ block of mass $m(=0.1 \ kg)$ is hanging over a frictionless light fixed pulley by an inextensible string of negligible mass. The other end of the string is pulled by a constant force $F$ in the vertically downward direction. The linear momentum of the block increases by $2 \ kg \ m/s$ in $1 \ s$ after the block starts from rest. Then, (given $g=10 \ m/s^2$):

$A$ body of mass $5\,kg$ rests on a rough horizontal surface of coefficient of friction $0.2$. The body is pulled through a distance of $10\,m$ by a horizontal force of $25\,N$. The kinetic energy acquired by it is ......... $J$.

$A$ bullet of mass $0.01 \,kg$ travelling at a speed of $500 \,ms^{-1}$ strikes a block of mass $2 \,kg$ which is suspended by a string of length $5 \,m$. The centre of gravity of the block is found to rise a vertical distance of $0.1 \,m$. What is the speed of the bullet after it emerges from the block (in $\,ms^{-1}$)?

$A$ ball of mass $1 \ kg$ moving with a velocity of $0.4 \ m/s$ collides with another ball of the same mass at rest. After the collision,the first ball moves with a velocity of $0.3 \ m/s$ in a direction perpendicular to the initial direction. Find the magnitude of the momentum $\vec{P}$ of the second ball in $kg \cdot m/s$.

$A$ ball loses $15.0\%$ of its kinetic energy when it bounces back from a concrete wall. With what speed must you throw it vertically down from a height of $12.4\, m$ to have it bounce back to the same height (ignore air resistance)? ............. $m / s$